diff --git a/src/Reactor/LLVMJIT.cpp b/src/Reactor/LLVMJIT.cpp
index eaee17b..910cea8 100644
--- a/src/Reactor/LLVMJIT.cpp
+++ b/src/Reactor/LLVMJIT.cpp
@@ -54,7 +54,11 @@
 #endif
 
 #if __has_feature(memory_sanitizer)
-#	include "sanitizer/msan_interface.h"  // TODO(b/155148722): Remove when we no longer unpoison all writes.
+
+// TODO(b/155148722): Remove when we no longer unpoison all writes.
+#	if !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION
+#		include "sanitizer/msan_interface.h"
+#	endif
 
 #	include <dlfcn.h>  // dlsym()
 
@@ -540,7 +544,11 @@
 #	endif
 #endif
 #if __has_feature(memory_sanitizer)
-			functions.try_emplace("msan_unpoison", reinterpret_cast<void *>(__msan_unpoison));  // TODO(b/155148722): Remove when we no longer unpoison all writes.
+
+// TODO(b/155148722): Remove when we no longer unpoison all writes.
+#	if !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION
+			functions.try_emplace("msan_unpoison", reinterpret_cast<void *>(__msan_unpoison));
+#	endif
 
 			functions.try_emplace("emutls_get_address", reinterpret_cast<void *>(rr::getTLSAddress));
 			functions.try_emplace("emutls_v.__msan_retval_tls", reinterpret_cast<void *>(static_cast<uintptr_t>(rr::MSanTLS::retval)));
diff --git a/src/Reactor/LLVMReactor.cpp b/src/Reactor/LLVMReactor.cpp
index b9bb3d7..506e5dc 100644
--- a/src/Reactor/LLVMReactor.cpp
+++ b/src/Reactor/LLVMReactor.cpp
@@ -985,7 +985,7 @@
 			auto elTy = T(type);
 			ASSERT(V(ptr)->getType()->getContainedType(0) == elTy);
 
-			if(__has_feature(memory_sanitizer))
+			if(__has_feature(memory_sanitizer) && !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION)
 			{
 				// Mark all memory writes as initialized by calling __msan_unpoison
 				// void __msan_unpoison(const volatile void *a, size_t size)
@@ -1091,7 +1091,7 @@
 	auto func = llvm::Intrinsic::getDeclaration(jit->module.get(), llvm::Intrinsic::masked_store, { elVecTy, elVecPtrTy });
 	jit->builder->CreateCall(func, { V(val), V(ptr), align, i1Mask });
 
-	if(__has_feature(memory_sanitizer))
+	if(__has_feature(memory_sanitizer) && !REACTOR_ENABLE_MEMORY_SANITIZER_INSTRUMENTATION)
 	{
 		// Mark memory writes as initialized by calling __msan_unpoison
 		// void __msan_unpoison(const volatile void *a, size_t size)