diff --git a/src/cgutils.cpp b/src/cgutils.cpp
index a87a217f9b067..cce8408b1e11f 100644
--- a/src/cgutils.cpp
+++ b/src/cgutils.cpp
@@ -4505,23 +4505,23 @@ static jl_cgval_t emit_memorynew(jl_codectx_t &ctx, jl_datatype_t *typ, jl_cgval
 
     auto T_size = ctx.types().T_size;
     auto int8t = getInt8Ty(ctx.builder.getContext());
-    auto ptls = get_current_ptls(ctx);
-    BasicBlock *emptymemBB, *defaultBB, *retvalBB;
+    BasicBlock *emptymemBB, *nonemptymemBB, *retvalBB;
     emptymemBB = BasicBlock::Create(ctx.builder.getContext(), "emptymem");
-    defaultBB = BasicBlock::Create(ctx.builder.getContext(), "default");
+    nonemptymemBB = BasicBlock::Create(ctx.builder.getContext(), "nonemptymem");
     retvalBB = BasicBlock::Create(ctx.builder.getContext(), "retval");
     auto nel_unboxed = emit_unbox(ctx, ctx.types().T_size, nel, (jl_value_t*)jl_long_type);
     Value *memorynew_empty = ctx.builder.CreateICmpEQ(nel_unboxed, ConstantInt::get(T_size, 0));
     setName(ctx.emission_context, memorynew_empty, "memorynew_empty");
-    ctx.builder.CreateCondBr(memorynew_empty, emptymemBB, defaultBB);
+    ctx.builder.CreateCondBr(memorynew_empty, emptymemBB, nonemptymemBB);
     // if nel == 0
     emptymemBB->insertInto(ctx.f);
     ctx.builder.SetInsertPoint(emptymemBB);
-    auto emptyalloc =literal_pointer_val(ctx, (jl_value_t*)inst);
+    auto emptyalloc = literal_pointer_val(ctx, (jl_value_t*)inst);
     ctx.builder.CreateBr(retvalBB);
-    defaultBB->insertInto(ctx.f);
-    ctx.builder.SetInsertPoint(defaultBB);
+    nonemptymemBB->insertInto(ctx.f);
+    ctx.builder.SetInsertPoint(nonemptymemBB);
     // else actually allocate mem
+    auto ptls = get_current_ptls(ctx);
     auto arg_typename = [&] JL_NOTSAFEPOINT {
         std::string type_str;
         auto eltype = jl_tparam1(typ);
@@ -4537,10 +4537,12 @@ static jl_cgval_t emit_memorynew(jl_codectx_t &ctx, jl_datatype_t *typ, jl_cgval
     auto cg_elsz = ConstantInt::get(T_size, elsz);
 
     FunctionCallee intr = Intrinsic::getDeclaration(jl_Module, Intrinsic::smul_with_overflow, ArrayRef<Type*>(T_size));
+    // compute nbytes with possible overflow
     Value *prod_with_overflow = ctx.builder.CreateCall(intr, {nel_unboxed, cg_elsz});
     Value *nbytes = ctx.builder.CreateExtractValue(prod_with_overflow, 0);
     Value *overflow = ctx.builder.CreateExtractValue(prod_with_overflow, 1);
     if (isunion) {
+		// if isunion, we need to allocate the union selector bytes as well
         intr = Intrinsic::getDeclaration(jl_Module, Intrinsic::sadd_with_overflow, ArrayRef<Type*>(T_size));
         Value *add_with_overflow = ctx.builder.CreateCall(intr, {nel_unboxed, nbytes});
         nbytes = ctx.builder.CreateExtractValue(add_with_overflow, 0);
@@ -4549,13 +4551,18 @@ static jl_cgval_t emit_memorynew(jl_codectx_t &ctx, jl_datatype_t *typ, jl_cgval
     }
     Value *notoverflow = ctx.builder.CreateNot(overflow);
     error_unless(ctx, notoverflow, "invalid GenericMemory size: too large for system address width");
-
+	// actually allocate (TODO: optimize alloc for fixed sizes)
     auto alloc = ctx.builder.CreateCall(prepare_call(jl_alloc_genericmemory_unchecked_func), { ptls, nbytes, cg_typ});
+    // set length (jl_alloc_genericmemory_unchecked_func doesn't have it)
     auto len_field = ctx.builder.CreateStructGEP(ctx.types().T_jlgenericmemory, alloc, 0);
     ctx.builder.CreateStore(nel_unboxed, len_field);
+    // zeroinit pointers and unions
     if (zi) {
         auto data_field = ctx.builder.CreateStructGEP(ctx.types().T_jlgenericmemory, alloc, 1);
-        ctx.builder.CreateMemSet(data_field, ConstantInt::get(int8t, 0), nbytes, Align(sizeof(void*)));
+        jl_value_t *ety = jl_tparam1(typ);
+        Type *elty = isboxed ? ctx.types().T_prjlvalue : julia_type_to_llvm(ctx, ety);
+        auto data = ctx.builder.CreateInBoundsGEP(elty, data_field, 0);
+        ctx.builder.CreateMemSet(data, ConstantInt::get(int8t, 0), nbytes, Align(sizeof(void*)));
     }
 
     setName(ctx.emission_context, alloc, arg_typename);
@@ -4565,8 +4572,8 @@ static jl_cgval_t emit_memorynew(jl_codectx_t &ctx, jl_datatype_t *typ, jl_cgval
     ctx.builder.SetInsertPoint(retvalBB);
     auto phi = ctx.builder.CreatePHI(ctx.types().T_prjlvalue, 2);
     phi->addIncoming(emptyalloc, emptymemBB);
-    phi->addIncoming(alloc, defaultBB);
-    //ctx.f->print(dbgs(), NULL);
+    phi->addIncoming(alloc, nonemptymemBB);
+    ctx.f->print(dbgs(), NULL);
     return mark_julia_type(ctx, phi, true, typ);
 }