diff --git a/flang/include/flang/Frontend/FrontendActions.h b/flang/include/flang/Frontend/FrontendActions.h
index 374fd76c8ae17..4e3d3cb2657db 100644
--- a/flang/include/flang/Frontend/FrontendActions.h
+++ b/flang/include/flang/Frontend/FrontendActions.h
@@ -19,6 +19,7 @@
 #include "flang/Semantics/semantics.h"
 
 #include "mlir/IR/BuiltinOps.h"
+#include "mlir/IR/OwningOpRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/IR/Module.h"
 #include <memory>
@@ -215,8 +216,8 @@ class CodeGenAction : public FrontendAction {
   CodeGenAction(BackendActionTy act) : action{act} {};
   /// @name MLIR
   /// {
-  std::unique_ptr<mlir::ModuleOp> mlirModule;
   std::unique_ptr<mlir::MLIRContext> mlirCtx;
+  mlir::OwningOpRef<mlir::ModuleOp> mlirModule;
   /// }
 
   /// @name LLVM IR
diff --git a/flang/include/flang/Lower/AbstractConverter.h b/flang/include/flang/Lower/AbstractConverter.h
index 8f026ac3280bf..607aff41f6459 100644
--- a/flang/include/flang/Lower/AbstractConverter.h
+++ b/flang/include/flang/Lower/AbstractConverter.h
@@ -62,7 +62,7 @@ struct SymbolBox;
 namespace pft {
 struct Variable;
 struct FunctionLikeUnit;
-}
+} // namespace pft
 
 using SomeExpr = Fortran::evaluate::Expr<Fortran::evaluate::SomeType>;
 using SymbolRef = Fortran::common::Reference<const Fortran::semantics::Symbol>;
@@ -295,7 +295,7 @@ class AbstractConverter {
   /// Get the OpBuilder
   virtual fir::FirOpBuilder &getFirOpBuilder() = 0;
   /// Get the ModuleOp
-  virtual mlir::ModuleOp &getModuleOp() = 0;
+  virtual mlir::ModuleOp getModuleOp() = 0;
   /// Get the MLIRContext
   virtual mlir::MLIRContext &getMLIRContext() = 0;
   /// Unique a symbol (add a containing scope specific prefix)
diff --git a/flang/include/flang/Lower/Bridge.h b/flang/include/flang/Lower/Bridge.h
index 8ea5ed52e2821..6404a16f7785a 100644
--- a/flang/include/flang/Lower/Bridge.h
+++ b/flang/include/flang/Lower/Bridge.h
@@ -23,6 +23,7 @@
 #include "flang/Optimizer/Builder/FIRBuilder.h"
 #include "flang/Optimizer/Dialect/Support/KindMapping.h"
 #include "mlir/IR/BuiltinOps.h"
+#include "mlir/IR/OwningOpRef.h"
 #include <set>
 
 namespace llvm {
@@ -83,7 +84,8 @@ class LoweringBridge {
   mlir::MLIRContext &getMLIRContext() { return context; }
 
   /// Get the ModuleOp. It can never be null, which is asserted in the ctor.
-  mlir::ModuleOp &getModule() { return *module.get(); }
+  mlir::ModuleOp getModule() { return *module; }
+  mlir::ModuleOp getModuleAndRelease() { return module.release(); }
 
   const Fortran::common::IntrinsicTypeDefaultKinds &getDefaultKinds() const {
     return defaultKinds;
@@ -166,7 +168,7 @@ class LoweringBridge {
   const Fortran::evaluate::TargetCharacteristics &targetCharacteristics;
   const Fortran::parser::AllCookedSources *cooked;
   mlir::MLIRContext &context;
-  std::unique_ptr<mlir::ModuleOp> module;
+  mlir::OwningOpRef<mlir::ModuleOp> module;
   fir::KindMapping &kindMap;
   const Fortran::lower::LoweringOptions &loweringOptions;
   const std::vector<Fortran::lower::EnvironmentDefault> &envDefaults;
diff --git a/flang/include/flang/Lower/OpenACC.h b/flang/include/flang/Lower/OpenACC.h
index fbf61e7184ae2..0d7038a7fd856 100644
--- a/flang/include/flang/Lower/OpenACC.h
+++ b/flang/include/flang/Lower/OpenACC.h
@@ -19,7 +19,7 @@ namespace llvm {
 template <typename T, unsigned N>
 class SmallVector;
 class StringRef;
-}
+} // namespace llvm
 
 namespace mlir {
 class Location;
@@ -44,7 +44,7 @@ struct OpenACCRoutineConstruct;
 namespace semantics {
 class SemanticsContext;
 class Symbol;
-}
+} // namespace semantics
 
 namespace lower {
 
@@ -78,11 +78,11 @@ void genOpenACCDeclarativeConstruct(AbstractConverter &,
                                     AccRoutineInfoMappingList &);
 void genOpenACCRoutineConstruct(AbstractConverter &,
                                 Fortran::semantics::SemanticsContext &,
-                                mlir::ModuleOp &,
+                                mlir::ModuleOp,
                                 const parser::OpenACCRoutineConstruct &,
                                 AccRoutineInfoMappingList &);
 
-void finalizeOpenACCRoutineAttachment(mlir::ModuleOp &,
+void finalizeOpenACCRoutineAttachment(mlir::ModuleOp,
                                       AccRoutineInfoMappingList &);
 
 /// Get a acc.private.recipe op for the given type or create it if it does not
diff --git a/flang/include/flang/Tools/CrossToolHelpers.h b/flang/include/flang/Tools/CrossToolHelpers.h
index c0091e1c953b8..0286f2aa14519 100644
--- a/flang/include/flang/Tools/CrossToolHelpers.h
+++ b/flang/include/flang/Tools/CrossToolHelpers.h
@@ -174,7 +174,7 @@ struct OffloadModuleOpts {
 //  Shares assinging of the OpenMP OffloadModuleInterface and its assorted
 //  attributes accross Flang tools (bbc/flang)
 [[maybe_unused]] static void setOffloadModuleInterfaceAttributes(
-    mlir::ModuleOp &module, OffloadModuleOpts Opts) {
+    mlir::ModuleOp module, OffloadModuleOpts Opts) {
   // Should be registered by the OpenMPDialect
   if (auto offloadMod = llvm::dyn_cast<mlir::omp::OffloadModuleInterface>(
           module.getOperation())) {
@@ -198,7 +198,7 @@ struct OffloadModuleOpts {
 }
 
 [[maybe_unused]] static void setOpenMPVersionAttribute(
-    mlir::ModuleOp &module, int64_t version) {
+    mlir::ModuleOp module, int64_t version) {
   module.getOperation()->setAttr(
       mlir::StringAttr::get(module.getContext(), llvm::Twine{"omp.version"}),
       mlir::omp::VersionAttr::get(module.getContext(), version));
diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
index 77631f70dfd19..603cb039d20b1 100644
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -149,7 +149,7 @@ bool PrescanAndSemaDebugAction::beginSourceFileAction() {
          (runSemanticChecks() || true) && (generateRtTypeTables() || true);
 }
 
-static void addDependentLibs(mlir::ModuleOp &mlirModule, CompilerInstance &ci) {
+static void addDependentLibs(mlir::ModuleOp mlirModule, CompilerInstance &ci) {
   const std::vector<std::string> &libs =
       ci.getInvocation().getCodeGenOpts().DependentLibs;
   if (libs.empty()) {
@@ -171,7 +171,7 @@ static void addDependentLibs(mlir::ModuleOp &mlirModule, CompilerInstance &ci) {
 // Add to MLIR code target specific items which are dependent on target
 // configuration specified by the user.
 // Clang equivalent function: AMDGPUTargetCodeGenInfo::emitTargetGlobals
-static void addAMDGPUSpecificMLIRItems(mlir::ModuleOp &mlirModule,
+static void addAMDGPUSpecificMLIRItems(mlir::ModuleOp mlirModule,
                                        CompilerInstance &ci) {
   const TargetOptions &targetOpts = ci.getInvocation().getTargetOpts();
   const llvm::Triple triple(targetOpts.triple);
@@ -269,7 +269,7 @@ bool CodeGenAction::beginSourceFileAction() {
       return false;
     }
 
-    mlirModule = std::make_unique<mlir::ModuleOp>(module.release());
+    mlirModule = std::move(module);
     const llvm::DataLayout &dl = targetMachine.createDataLayout();
     fir::support::setMLIRDataLayout(*mlirModule, dl);
     return true;
@@ -303,14 +303,11 @@ bool CodeGenAction::beginSourceFileAction() {
       ci.getInvocation().getFrontendOpts().features, targetMachine,
       ci.getInvocation().getTargetOpts(), ci.getInvocation().getCodeGenOpts());
 
-  // Fetch module from lb, so we can set
-  mlirModule = std::make_unique<mlir::ModuleOp>(lb.getModule());
-
   if (ci.getInvocation().getFrontendOpts().features.IsEnabled(
           Fortran::common::LanguageFeature::OpenMP)) {
-    setOffloadModuleInterfaceAttributes(*mlirModule,
+    setOffloadModuleInterfaceAttributes(lb.getModule(),
                                         ci.getInvocation().getLangOpts());
-    setOpenMPVersionAttribute(*mlirModule,
+    setOpenMPVersionAttribute(lb.getModule(),
                               ci.getInvocation().getLangOpts().OpenMPVersion);
   }
 
@@ -318,6 +315,9 @@ bool CodeGenAction::beginSourceFileAction() {
   Fortran::parser::Program &parseTree{*ci.getParsing().parseTree()};
   lb.lower(parseTree, ci.getSemanticsContext());
 
+  // Fetch module from lb, so we can set
+  mlirModule = lb.getModuleAndRelease();
+
   // Add target specific items like dependent libraries, target specific
   // constants etc.
   addDependentLibs(*mlirModule, ci);
@@ -961,6 +961,9 @@ static void generateMachineCodeOrAssemblyImpl(clang::DiagnosticsEngine &diags,
 
   // Run the passes
   codeGenPasses.run(llvmModule);
+
+  // Cleanup
+  delete tlii;
 }
 
 void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
@@ -1043,6 +1046,9 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
 
   // Run the passes.
   mpm.run(*llvmModule, mam);
+
+  // Cleanup
+  delete tlii;
 }
 
 // This class handles optimization remark messages requested if
diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index 17b794d147c6f..c7e2635230e98 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -1028,7 +1028,7 @@ class FirConverter : public Fortran::lower::AbstractConverter {
 
   fir::FirOpBuilder &getFirOpBuilder() override final { return *builder; }
 
-  mlir::ModuleOp &getModuleOp() override final { return bridge.getModule(); }
+  mlir::ModuleOp getModuleOp() override final { return bridge.getModule(); }
 
   mlir::MLIRContext &getMLIRContext() override final {
     return bridge.getMLIRContext();
@@ -6137,10 +6137,7 @@ void Fortran::lower::LoweringBridge::lower(
 }
 
 void Fortran::lower::LoweringBridge::parseSourceFile(llvm::SourceMgr &srcMgr) {
-  mlir::OwningOpRef<mlir::ModuleOp> owningRef =
-      mlir::parseSourceFile<mlir::ModuleOp>(srcMgr, &context);
-  module.reset(new mlir::ModuleOp(owningRef.get().getOperation()));
-  owningRef.release();
+  module = mlir::parseSourceFile<mlir::ModuleOp>(srcMgr, &context);
 }
 
 Fortran::lower::LoweringBridge::LoweringBridge(
@@ -6207,19 +6204,18 @@ Fortran::lower::LoweringBridge::LoweringBridge(
   };
 
   // Create the module and attach the attributes.
-  module = std::make_unique<mlir::ModuleOp>(
+  module = mlir::OwningOpRef<mlir::ModuleOp>(
       mlir::ModuleOp::create(getPathLocation()));
-  assert(module.get() && "module was not created");
-  fir::setTargetTriple(*module.get(), triple);
-  fir::setKindMapping(*module.get(), kindMap);
-  fir::setTargetCPU(*module.get(), targetMachine.getTargetCPU());
-  fir::setTuneCPU(*module.get(), targetOpts.cpuToTuneFor);
-  fir::setTargetFeatures(*module.get(), targetMachine.getTargetFeatureString());
-  fir::support::setMLIRDataLayout(*module.get(),
-                                  targetMachine.createDataLayout());
-  fir::setIdent(*module.get(), Fortran::common::getFlangFullVersion());
+  assert(*module && "module was not created");
+  fir::setTargetTriple(*module, triple);
+  fir::setKindMapping(*module, kindMap);
+  fir::setTargetCPU(*module, targetMachine.getTargetCPU());
+  fir::setTuneCPU(*module, targetOpts.cpuToTuneFor);
+  fir::setTargetFeatures(*module, targetMachine.getTargetFeatureString());
+  fir::support::setMLIRDataLayout(*module, targetMachine.createDataLayout());
+  fir::setIdent(*module, Fortran::common::getFlangFullVersion());
   if (cgOpts.RecordCommandLine)
-    fir::setCommandline(*module.get(), *cgOpts.RecordCommandLine);
+    fir::setCommandline(*module, *cgOpts.RecordCommandLine);
 }
 
 void Fortran::lower::genCleanUpInRegionIfAny(
diff --git a/flang/lib/Lower/OpenACC.cpp b/flang/lib/Lower/OpenACC.cpp
index ed18ad89c16ef..8155c36396b11 100644
--- a/flang/lib/Lower/OpenACC.cpp
+++ b/flang/lib/Lower/OpenACC.cpp
@@ -2670,11 +2670,13 @@ static void genACCDataOp(Fortran::lower::AbstractConverter &converter,
           asyncOnlyDeviceTypes);
       attachEntryOperands.append(dataClauseOperands.begin() + crtDataStart,
                                  dataClauseOperands.end());
-    } else if(const auto *defaultClause = 
-                  std::get_if<Fortran::parser::AccClause::Default>(&clause.u)) {
+    } else if (const auto *defaultClause =
+                   std::get_if<Fortran::parser::AccClause::Default>(
+                       &clause.u)) {
       if ((defaultClause->v).v == llvm::acc::DefaultValue::ACC_Default_none)
         hasDefaultNone = true;
-      else if ((defaultClause->v).v == llvm::acc::DefaultValue::ACC_Default_present)
+      else if ((defaultClause->v).v ==
+               llvm::acc::DefaultValue::ACC_Default_present)
         hasDefaultPresent = true;
     }
   }
@@ -3830,7 +3832,7 @@ genDeclareInFunction(Fortran::lower::AbstractConverter &converter,
 
 static void
 genDeclareInModule(Fortran::lower::AbstractConverter &converter,
-                   mlir::ModuleOp &moduleOp,
+                   mlir::ModuleOp moduleOp,
                    const Fortran::parser::AccClauseList &accClauseList) {
   mlir::OpBuilder modBuilder(moduleOp.getBodyRegion());
   for (const Fortran::parser::AccClause &clause : accClauseList.v) {
@@ -3981,7 +3983,7 @@ static void attachRoutineInfo(mlir::func::FuncOp func,
 
 void Fortran::lower::genOpenACCRoutineConstruct(
     Fortran::lower::AbstractConverter &converter,
-    Fortran::semantics::SemanticsContext &semanticsContext, mlir::ModuleOp &mod,
+    Fortran::semantics::SemanticsContext &semanticsContext, mlir::ModuleOp mod,
     const Fortran::parser::OpenACCRoutineConstruct &routineConstruct,
     Fortran::lower::AccRoutineInfoMappingList &accRoutineInfos) {
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
@@ -4139,7 +4141,7 @@ void Fortran::lower::genOpenACCRoutineConstruct(
 }
 
 void Fortran::lower::finalizeOpenACCRoutineAttachment(
-    mlir::ModuleOp &mod,
+    mlir::ModuleOp mod,
     Fortran::lower::AccRoutineInfoMappingList &accRoutineInfos) {
   for (auto &mapping : accRoutineInfos) {
     mlir::func::FuncOp funcOp =
diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
index 926f83b9c9a64..4edea86b417c3 100644
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -3087,7 +3087,7 @@ struct GlobalOpConversion : public fir::FIROpConversion<fir::GlobalOp> {
 private:
   static void addComdat(mlir::LLVM::GlobalOp &global,
                         mlir::ConversionPatternRewriter &rewriter,
-                        mlir::ModuleOp &module) {
+                        mlir::ModuleOp module) {
     const char *comdatName = "__llvm_comdat";
     mlir::LLVM::ComdatOp comdatOp =
         module.lookupSymbol<mlir::LLVM::ComdatOp>(comdatName);
diff --git a/flang/unittests/Frontend/CodeGenActionTest.cpp b/flang/unittests/Frontend/CodeGenActionTest.cpp
index 5d75de03d4e55..e9ff095973b97 100644
--- a/flang/unittests/Frontend/CodeGenActionTest.cpp
+++ b/flang/unittests/Frontend/CodeGenActionTest.cpp
@@ -72,8 +72,7 @@ class LLVMConversionFailureCodeGenAction : public CodeGenAction {
     mlirCtx->loadDialect<test::DummyDialect>();
 
     mlir::Location loc(mlir::UnknownLoc::get(mlirCtx.get()));
-    mlirModule =
-        std::make_unique<mlir::ModuleOp>(mlir::ModuleOp::create(loc, "mod"));
+    mlirModule = mlir::ModuleOp::create(loc, "mod");
 
     mlir::OpBuilder builder(mlirCtx.get());
     builder.setInsertionPointToStart(&mlirModule->getRegion().front());
diff --git a/flang/unittests/Optimizer/Builder/CharacterTest.cpp b/flang/unittests/Optimizer/Builder/CharacterTest.cpp
index c6defcd51095b..6d912b81d9541 100644
--- a/flang/unittests/Optimizer/Builder/CharacterTest.cpp
+++ b/flang/unittests/Optimizer/Builder/CharacterTest.cpp
@@ -26,19 +26,20 @@ struct CharacterTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
-    mlir::func::FuncOp func = mlir::func::FuncOp::create(
+    moduleOp = builder.create<mlir::ModuleOp>(loc);
+    builder.setInsertionPointToStart(moduleOp->getBody());
+    mlir::func::FuncOp func = builder.create<mlir::func::FuncOp>(
         loc, "func1", builder.getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder.setInsertionPointToStart(entryBlock);
 
-    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, *kindMap);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(builder, *kindMap);
   }
 
   fir::FirOpBuilder &getBuilder() { return *firBuilder; }
 
   mlir::MLIRContext context;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
   std::unique_ptr<fir::KindMapping> kindMap;
   std::unique_ptr<fir::FirOpBuilder> firBuilder;
 };
diff --git a/flang/unittests/Optimizer/Builder/ComplexTest.cpp b/flang/unittests/Optimizer/Builder/ComplexTest.cpp
index 6472a52f25ee5..eefab118e255a 100644
--- a/flang/unittests/Optimizer/Builder/ComplexTest.cpp
+++ b/flang/unittests/Optimizer/Builder/ComplexTest.cpp
@@ -22,15 +22,15 @@ struct ComplexTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
-    mlir::func::FuncOp func = mlir::func::FuncOp::create(
+    moduleOp = builder.create<mlir::ModuleOp>(loc);
+    builder.setInsertionPointToStart(moduleOp->getBody());
+    mlir::func::FuncOp func = builder.create<mlir::func::FuncOp>(
         loc, "func1", builder.getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder.setInsertionPointToStart(entryBlock);
 
     kindMap = std::make_unique<fir::KindMapping>(&context);
-    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, *kindMap);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(builder, *kindMap);
     helper = std::make_unique<fir::factory::Complex>(*firBuilder, loc);
 
     // Init commonly used types
@@ -46,6 +46,7 @@ struct ComplexTest : public testing::Test {
   }
 
   mlir::MLIRContext context;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
   std::unique_ptr<fir::KindMapping> kindMap;
   std::unique_ptr<fir::FirOpBuilder> firBuilder;
   std::unique_ptr<fir::factory::Complex> helper;
diff --git a/flang/unittests/Optimizer/Builder/FIRBuilderTest.cpp b/flang/unittests/Optimizer/Builder/FIRBuilderTest.cpp
index f63afe4137683..05407d96998a2 100644
--- a/flang/unittests/Optimizer/Builder/FIRBuilderTest.cpp
+++ b/flang/unittests/Optimizer/Builder/FIRBuilderTest.cpp
@@ -26,19 +26,20 @@ struct FIRBuilderTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
-    mlir::func::FuncOp func = mlir::func::FuncOp::create(
+    moduleOp = builder.create<mlir::ModuleOp>(loc);
+    builder.setInsertionPointToStart(moduleOp->getBody());
+    mlir::func::FuncOp func = builder.create<mlir::func::FuncOp>(
         loc, "func1", builder.getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder.setInsertionPointToStart(entryBlock);
 
-    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, kindMap);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(builder, kindMap);
   }
 
   fir::FirOpBuilder &getBuilder() { return *firBuilder; }
 
   mlir::MLIRContext context;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
   std::unique_ptr<fir::FirOpBuilder> firBuilder;
 };
 
diff --git a/flang/unittests/Optimizer/Builder/HLFIRToolsTest.cpp b/flang/unittests/Optimizer/Builder/HLFIRToolsTest.cpp
index 1858b276f1fc3..640b7ecc1e565 100644
--- a/flang/unittests/Optimizer/Builder/HLFIRToolsTest.cpp
+++ b/flang/unittests/Optimizer/Builder/HLFIRToolsTest.cpp
@@ -25,14 +25,14 @@ struct HLFIRToolsTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
-    mlir::func::FuncOp func = mlir::func::FuncOp::create(
+    moduleOp = builder.create<mlir::ModuleOp>(loc);
+    builder.setInsertionPointToStart(moduleOp->getBody());
+    mlir::func::FuncOp func = builder.create<mlir::func::FuncOp>(
         loc, "func1", builder.getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder.setInsertionPointToStart(entryBlock);
 
-    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, kindMap);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(builder, kindMap);
   }
 
   mlir::Value createDeclare(fir::ExtendedValue exv) {
@@ -52,6 +52,7 @@ struct HLFIRToolsTest : public testing::Test {
 
   int varCounter = 0;
   mlir::MLIRContext context;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
   std::unique_ptr<fir::FirOpBuilder> firBuilder;
 };
 
diff --git a/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h b/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h
index d0ec97733e83d..40abf567400b3 100644
--- a/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h
+++ b/flang/unittests/Optimizer/Builder/Runtime/RuntimeCallTestBase.h
@@ -24,16 +24,16 @@ struct RuntimeCallTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder.create<mlir::ModuleOp>(loc);
+    moduleOp = builder.create<mlir::ModuleOp>(loc);
+    builder.setInsertionPointToStart(moduleOp->getBody());
     mlir::func::FuncOp func =
-        mlir::func::FuncOp::create(loc, "runtime_unit_tests_func",
+        builder.create<mlir::func::FuncOp>(loc, "runtime_unit_tests_func",
             builder.getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder.setInsertionPointToStart(entryBlock);
 
     kindMap = std::make_unique<fir::KindMapping>(&context);
-    firBuilder = std::make_unique<fir::FirOpBuilder>(mod, *kindMap);
+    firBuilder = std::make_unique<fir::FirOpBuilder>(builder, *kindMap);
 
     i1Ty = firBuilder->getI1Type();
     i8Ty = firBuilder->getI8Type();
@@ -66,6 +66,7 @@ struct RuntimeCallTest : public testing::Test {
   }
 
   mlir::MLIRContext context;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
   std::unique_ptr<fir::KindMapping> kindMap;
   std::unique_ptr<fir::FirOpBuilder> firBuilder;
 
diff --git a/flang/unittests/Optimizer/FortranVariableTest.cpp b/flang/unittests/Optimizer/FortranVariableTest.cpp
index 87efb624735cf..4ba9359a07e4d 100644
--- a/flang/unittests/Optimizer/FortranVariableTest.cpp
+++ b/flang/unittests/Optimizer/FortranVariableTest.cpp
@@ -19,12 +19,12 @@ struct FortranVariableTest : public testing::Test {
 
     // Set up a Module with a dummy function operation inside.
     // Set the insertion point in the function entry block.
-    mlir::ModuleOp mod = builder->create<mlir::ModuleOp>(loc);
+    moduleOp = builder->create<mlir::ModuleOp>(loc);
+    builder->setInsertionPointToStart(moduleOp->getBody());
     mlir::func::FuncOp func =
-        mlir::func::FuncOp::create(loc, "fortran_variable_tests",
+        builder->create<mlir::func::FuncOp>(loc, "fortran_variable_tests",
             builder->getFunctionType(std::nullopt, std::nullopt));
     auto *entryBlock = func.addEntryBlock();
-    mod.push_back(mod);
     builder->setInsertionPointToStart(entryBlock);
   }
 
@@ -40,6 +40,7 @@ struct FortranVariableTest : public testing::Test {
   }
   mlir::MLIRContext context;
   std::unique_ptr<mlir::OpBuilder> builder;
+  mlir::OwningOpRef<mlir::ModuleOp> moduleOp;
 };
 
 TEST_F(FortranVariableTest, SimpleScalar) {
diff --git a/flang/unittests/Runtime/ArrayConstructor.cpp b/flang/unittests/Runtime/ArrayConstructor.cpp
index 62e3b780a27e7..53774a0eea07d 100644
--- a/flang/unittests/Runtime/ArrayConstructor.cpp
+++ b/flang/unittests/Runtime/ArrayConstructor.cpp
@@ -127,6 +127,9 @@ TEST(ArrayConstructor, Character) {
       0);
   result.Deallocate();
   cookieAllocator.deallocate(acVector, 1);
+  x->Deallocate();
+  y->Deallocate();
+  c->Deallocate();
 }
 
 TEST(ArrayConstructor, CharacterRuntimeCheck) {
diff --git a/flang/unittests/Runtime/CharacterTest.cpp b/flang/unittests/Runtime/CharacterTest.cpp
index e54fd8a5075f6..d462c9120fd8c 100644
--- a/flang/unittests/Runtime/CharacterTest.cpp
+++ b/flang/unittests/Runtime/CharacterTest.cpp
@@ -259,6 +259,9 @@ void RunExtremumTests(const char *which,
           t.expect[i], t.expect[i] + std::strlen(t.expect[i])};
       EXPECT_EQ(expect, got) << "inputs: '" << t.x[i] << "','" << t.y[i] << "'";
     }
+
+    x->Deallocate();
+    y->Deallocate();
   }
 }