diff --git a/libevmjit/Array.cpp b/libevmjit/Array.cpp
index e77ceefe4..96329afd5 100644
--- a/libevmjit/Array.cpp
+++ b/libevmjit/Array.cpp
@@ -8,8 +8,6 @@
 #include "RuntimeManager.h"
 #include "Utils.h"
 
-#include <set> // DEBUG only
-
 namespace dev
 {
 namespace eth
@@ -266,52 +264,15 @@ void Array::extend(llvm::Value* _arrayPtr, llvm::Value* _size)
 }
 }
 
-namespace
-{
-	struct AllocatedMemoryWatchdog
-	{
-		std::set<void*> allocatedMemory;
-
-		~AllocatedMemoryWatchdog()
-		{
-			if (!allocatedMemory.empty())
-			{
-				DLOG(mem) << allocatedMemory.size() << " MEM LEAKS!\n";
-				for (auto&& leak : allocatedMemory)
-					DLOG(mem) << "\t" << leak << "\n";
-			}
-		}
-	};
-
-	AllocatedMemoryWatchdog watchdog;
-}
-
 extern "C"
 {
-	using namespace dev::eth::jit;
-
 	EXPORT void* ext_realloc(void* _data, size_t _size) noexcept
 	{
-		//std::cerr << "REALLOC: " << _data << " [" << _size << "]" << std::endl;
-		auto newData = std::realloc(_data, _size);
-		if (_data != newData)
-		{
-			DLOG(mem) << "REALLOC: " << newData << " <- " << _data << " [" << _size << "]\n";
-			watchdog.allocatedMemory.erase(_data);
-			watchdog.allocatedMemory.insert(newData);
-		}
-		return newData;
+		return std::realloc(_data, _size);
 	}
 
 	EXPORT void ext_free(void* _data) noexcept
 	{
 		std::free(_data);
-		if (_data)
-		{
-			DLOG(mem) << "FREE   : " << _data << "\n";
-			watchdog.allocatedMemory.erase(_data);
-		}
 	}
-
-} // extern "C"
-
+}
diff --git a/libevmjit/Cache.cpp b/libevmjit/Cache.cpp
index 0e19b6276..01b1c8766 100644
--- a/libevmjit/Cache.cpp
+++ b/libevmjit/Cache.cpp
@@ -1,5 +1,7 @@
 #include "Cache.h"
 
+#include <mutex>
+
 #include "preprocessor/llvm_includes_start.h"
 #include <llvm/IR/Module.h>
 #include <llvm/IR/LLVMContext.h>
@@ -21,6 +23,8 @@ namespace evmjit
 
 namespace
 {
+	using Guard = std::lock_guard<std::mutex>;
+	std::mutex x_cacheMutex;
 	CacheMode g_mode;
 	std::unique_ptr<llvm::MemoryBuffer> g_lastObject;
 	JITListener* g_listener;
@@ -40,6 +44,8 @@ namespace
 
 ObjectCache* Cache::init(CacheMode _mode, JITListener* _listener)
 {
+	Guard g{x_cacheMutex};
+
 	g_mode = _mode;
 	g_listener = _listener;
 
@@ -59,6 +65,8 @@ ObjectCache* Cache::init(CacheMode _mode, JITListener* _listener)
 
 void Cache::clear()
 {
+	Guard g{x_cacheMutex};
+
 	using namespace llvm::sys;
 	llvm::SmallString<256> cachePath;
 	path::system_temp_directory(false, cachePath);
@@ -71,6 +79,8 @@ void Cache::clear()
 
 void Cache::preload(llvm::ExecutionEngine& _ee, std::unordered_map<std::string, uint64_t>& _funcCache)
 {
+	Guard g{x_cacheMutex};
+
 	// TODO: Cache dir should be in one place
 	using namespace llvm::sys;
 	llvm::SmallString<256> cachePath;
@@ -100,11 +110,14 @@ void Cache::preload(llvm::ExecutionEngine& _ee, std::unordered_map<std::string,
 
 std::unique_ptr<llvm::Module> Cache::getObject(std::string const& id)
 {
+	Guard g{x_cacheMutex};
+
 	if (g_mode != CacheMode::on && g_mode != CacheMode::read)
 		return nullptr;
 
-	if (g_listener)
-		g_listener->stateChanged(ExecState::CacheLoad);
+	// TODO: Disabled because is not thread-safe.
+	//if (g_listener)
+	//	g_listener->stateChanged(ExecState::CacheLoad);
 
 	DLOG(cache) << id << ": search\n";
 	if (!CHECK(!g_lastObject))
@@ -144,12 +157,15 @@ std::unique_ptr<llvm::Module> Cache::getObject(std::string const& id)
 
 void ObjectCache::notifyObjectCompiled(llvm::Module const* _module, llvm::MemoryBufferRef _object)
 {
+	Guard g{x_cacheMutex};
+
 	// Only in "on" and "write" mode
 	if (g_mode != CacheMode::on && g_mode != CacheMode::write)
 		return;
 
-	if (g_listener)
-		g_listener->stateChanged(ExecState::CacheWrite);
+	// TODO: Disabled because is not thread-safe.
+	// if (g_listener)
+		// g_listener->stateChanged(ExecState::CacheWrite);
 
 	auto&& id = _module->getModuleIdentifier();
 	llvm::SmallString<256> cachePath;
@@ -169,6 +185,8 @@ void ObjectCache::notifyObjectCompiled(llvm::Module const* _module, llvm::Memory
 
 std::unique_ptr<llvm::MemoryBuffer> ObjectCache::getObject(llvm::Module const* _module)
 {
+	Guard g{x_cacheMutex};
+
 	DLOG(cache) << _module->getModuleIdentifier() << ": use\n";
 	return std::move(g_lastObject);
 }