diff --git a/src/OpenGL/common/Image.cpp b/src/OpenGL/common/Image.cpp
index cfed057..61d91db 100644
--- a/src/OpenGL/common/Image.cpp
+++ b/src/OpenGL/common/Image.cpp
@@ -1189,7 +1189,11 @@
 			: Image(width, height, format, type, pitchP) {}
 		ImageImplementation(GLsizei width, GLsizei height, sw::Format internalFormat, int multiSampleDepth, bool lockable)
 			: Image(width, height, internalFormat, multiSampleDepth, lockable) {}
-		~ImageImplementation() override {}
+
+		~ImageImplementation() override
+		{
+			sync();   // Wait for any threads that use this image to finish.
+		}
 
 		void *lockInternal(int x, int y, int z, sw::Lock lock, sw::Accessor client) override
 		{
@@ -1229,7 +1233,9 @@
 
 	Image::~Image()
 	{
-		sync();   // Wait for any threads that use this image to finish.
+		// sync() must be called in the destructor of the most derived class to ensure their vtable isn't destroyed
+		// before all threads are done using this image. Image itself is abstract so it can't be the most derived.
+		ASSERT(isUnlocked());
 
 		if(parentTexture)
 		{
diff --git a/src/Renderer/Surface.cpp b/src/Renderer/Surface.cpp
index f29aaae..e964584 100644
--- a/src/Renderer/Surface.cpp
+++ b/src/Renderer/Surface.cpp
@@ -1301,9 +1301,7 @@
 	{
 		// sync() must be called before this destructor to ensure all locks have been released.
 		// We can't call it here because the parent resource may already have been destroyed.
-		ASSERT(external.lock == LOCK_UNLOCKED);
-		ASSERT(internal.lock == LOCK_UNLOCKED);
-		ASSERT(stencil.lock == LOCK_UNLOCKED);
+		ASSERT(isUnlocked());
 
 		if(!hasParent)
 		{
@@ -1371,9 +1369,9 @@
 
 	void Surface::unlockExternal()
 	{
-		resource->unlock();
-
 		external.unlockRect();
+
+		resource->unlock();
 	}
 
 	void *Surface::lockInternal(int x, int y, int z, Lock lock, Accessor client)
@@ -1455,9 +1453,9 @@
 
 	void Surface::unlockInternal()
 	{
-		resource->unlock();
-
 		internal.unlockRect();
+
+		resource->unlock();
 	}
 
 	void *Surface::lockStencil(int x, int y, int front, Accessor client)
@@ -1474,9 +1472,9 @@
 
 	void Surface::unlockStencil()
 	{
-		resource->unlock();
-
 		stencil.unlockRect();
+
+		resource->unlock();
 	}
 
 	int Surface::bytes(Format format)
diff --git a/src/Renderer/Surface.hpp b/src/Renderer/Surface.hpp
index 16ff78c..b54565e 100644
--- a/src/Renderer/Surface.hpp
+++ b/src/Renderer/Surface.hpp
@@ -293,7 +293,8 @@
 		inline int getStencilPitchB() const;
 		inline int getStencilSliceB() const;
 
-		void sync();   // Wait for lock(s) to be released
+		void sync();                      // Wait for lock(s) to be released.
+		inline bool isUnlocked() const;   // Only reliable after sync().
 
 		inline int getMultiSampleCount() const;
 		inline int getSuperSampleCount() const;
@@ -608,6 +609,13 @@
 		return internal.depth > 4 ? internal.depth / 4 : 1;
 	}
 
+	bool Surface::isUnlocked() const
+	{
+		return external.lock == LOCK_UNLOCKED &&
+		       internal.lock == LOCK_UNLOCKED &&
+		       stencil.lock == LOCK_UNLOCKED;
+	}
+
 	bool Surface::isExternalDirty() const
 	{
 		return external.buffer && external.buffer != internal.buffer && external.dirty;