diff --git a/src/thread/win32/SDL_syssem.c b/src/thread/win32/SDL_syssem.c
index c7a1bfd53..ac2648419 100644
--- a/src/thread/win32/SDL_syssem.c
+++ b/src/thread/win32/SDL_syssem.c
@@ -105,7 +105,7 @@ int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
 	switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
 #endif
 	    case WAIT_OBJECT_0:
-		--sem->count;
+		InterlockedDecrement(&sem->count);
 		retval = 0;
 		break;
 	    case WAIT_TIMEOUT:
@@ -150,13 +150,13 @@ int SDL_SemPost(SDL_sem *sem)
 	 * immediately get destroyed by another thread which
 	 * is waiting for this semaphore.
 	 */
-	++sem->count;
+	InterlockedIncrement(&sem->count);
 #if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
 	if ( ReleaseSemaphoreCE(sem->id, 1, NULL) == FALSE ) {
 #else
 	if ( ReleaseSemaphore(sem->id, 1, NULL) == FALSE ) {
 #endif
-		--sem->count;	/* restore */
+		InterlockedDecrement(&sem->count);	/* restore */
 		SDL_SetError("ReleaseSemaphore() failed");
 		return -1;
 	}