diff --git a/TSRM/tsrm_win32.c b/TSRM/tsrm_win32.c
index 0a299786287..84d153956e4 100644
--- a/TSRM/tsrm_win32.c
+++ b/TSRM/tsrm_win32.c
@@ -725,7 +725,6 @@ TSRM_API int shmget(key_t key, size_t size, int flags)
 TSRM_API void *shmat(int key, const void *shmaddr, int flags)
 {
 	shm_pair *shm = shm_get(key, NULL);
-	int err;
 
 	if (!shm->segment) {
 		return (void*)-1;
@@ -733,8 +732,8 @@ TSRM_API void *shmat(int key, const void *shmaddr, int flags)
 
 	shm->addr = MapViewOfFileEx(shm->segment, FILE_MAP_ALL_ACCESS, 0, 0, 0, NULL);
 
-	err = GetLastError();
-	if (err) {
+	if (NULL == shm->addr) {
+		int err = GetLastError();
 		SET_ERRNO_FROM_WIN32_CODE(err);
 		return (void*)-1;
 	}