diff --git a/src/function_builder.rs b/src/function_builder.rs
index b708adad..76d4143c 100644
--- a/src/function_builder.rs
+++ b/src/function_builder.rs
@@ -150,14 +150,14 @@ impl FunctionBuilder {
     /// let function_id = builder.finish(vec![], &mut module.funcs);
     /// # let _ = function_id;
     /// ```
-    pub fn finish(self, args: Vec<LocalId>, funcs: &mut ModuleFunctions) -> FunctionId {
-        let func = LocalFunction::new(args, self);
+    pub fn finish(self, args: Vec<LocalId>, locals: Vec<LocalId>, funcs: &mut ModuleFunctions) -> FunctionId {
+        let func = LocalFunction::new(args, locals, self);
         funcs.add_local(func)
     }
 
     /// Returns the [crate::LocalFunction] built by this builder.
-    pub fn local_func(self, args: Vec<LocalId>) -> LocalFunction {
-        LocalFunction::new(args, self)
+    pub fn local_func(self, args: Vec<LocalId>, locals: Vec<LocalId>) -> LocalFunction {
+        LocalFunction::new(args, locals, self)
     }
 }
 
diff --git a/src/module/data.rs b/src/module/data.rs
index 58acd1d6..943ca6c6 100644
--- a/src/module/data.rs
+++ b/src/module/data.rs
@@ -28,7 +28,7 @@ pub struct Data {
 }
 
 /// The kind of data segment: passive or active.
-#[derive(Debug)]
+#[derive(Clone, Copy, Debug)]
 pub enum DataKind {
     /// An active data segment that is automatically initialized at some address
     /// in a static memory.
@@ -41,7 +41,7 @@ pub enum DataKind {
 }
 
 /// The parts of a data segment that are only present in active data segments.
-#[derive(Clone, Debug)]
+#[derive(Clone, Copy, Debug)]
 pub struct ActiveData {
     /// The memory that this active data segment will be automatically
     /// initialized in.
diff --git a/src/module/functions/local_function/mod.rs b/src/module/functions/local_function/mod.rs
index c4507c9d..08327d94 100644
--- a/src/module/functions/local_function/mod.rs
+++ b/src/module/functions/local_function/mod.rs
@@ -21,6 +21,9 @@ pub struct LocalFunction {
 
     /// Arguments to this function, and the locals that they're assigned to.
     pub args: Vec<LocalId>,
+
+    /// Locals of this function, excluding arguments.
+    pub locals: Vec<LocalId>,
     //
     // TODO: provenance: (InstrSeqId, usize) -> offset in code section of the
     // original instruction. This will be necessary for preserving debug info.
@@ -28,8 +31,8 @@ pub struct LocalFunction {
 
 impl LocalFunction {
     /// Creates a new definition of a local function from its components.
-    pub(crate) fn new(args: Vec<LocalId>, builder: FunctionBuilder) -> LocalFunction {
-        LocalFunction { args, builder }
+    pub(crate) fn new(args: Vec<LocalId>, locals: Vec<LocalId>, builder: FunctionBuilder) -> LocalFunction {
+        LocalFunction { args, locals, builder }
     }
 
     /// Construct a new `LocalFunction`.
@@ -42,6 +45,7 @@ impl LocalFunction {
         id: FunctionId,
         ty: TypeId,
         args: Vec<LocalId>,
+        locals: Vec<LocalId>,
         mut body: wasmparser::BinaryReader<'_>,
         on_instr_pos: Option<&(dyn Fn(&usize) -> InstrLocId + Sync + Send + 'static)>,
         mut validator: FuncValidator<ValidatorResources>,
@@ -49,6 +53,7 @@ impl LocalFunction {
         let mut func = LocalFunction {
             builder: FunctionBuilder::without_entry(ty),
             args,
+            locals,
         };
 
         let result: Vec<_> = module.types.get(ty).results().iter().cloned().collect();
diff --git a/src/module/functions/mod.rs b/src/module/functions/mod.rs
index e782240b..c5cbfcba 100644
--- a/src/module/functions/mod.rs
+++ b/src/module/functions/mod.rs
@@ -366,6 +366,7 @@ impl Module {
 
             // Next up comes all the locals of the function.
             let mut reader = body.get_binary_reader();
+            let mut locals = Vec::new();
             for _ in 0..reader.read_var_u32()? {
                 let pos = reader.original_position();
                 let count = reader.read_var_u32()?;
@@ -375,6 +376,7 @@ impl Module {
                 for _ in 0..count {
                     let local_id = self.locals.add(ty);
                     let idx = indices.push_local(id, local_id);
+                    locals.push(local_id);
                     if self.config.generate_synthetic_names_for_anonymous_items {
                         let name = format!("l{}", idx);
                         self.locals.get_mut(local_id).name = Some(name);
@@ -382,13 +384,13 @@ impl Module {
                 }
             }
 
-            bodies.push((id, reader, args, ty, validator));
+            bodies.push((id, reader, args, locals, ty, validator));
         }
 
         // Wasm modules can often have a lot of functions and this operation can
         // take some time, so parse all function bodies in parallel.
         let results = maybe_parallel!(bodies.(into_iter | into_par_iter))
-            .map(|(id, body, args, ty, validator)| {
+            .map(|(id, body, args, locals, ty, validator)| {
                 (
                     id,
                     LocalFunction::parse(
@@ -397,6 +399,7 @@ impl Module {
                         id,
                         ty,
                         args,
+                        locals,
                         body,
                         on_instr_pos,
                         validator,