diff --git a/libretro-common/memmap/memmap.c b/libretro-common/memmap/memmap.c
index 3ea7092485..4b413c1449 100644
--- a/libretro-common/memmap/memmap.c
+++ b/libretro-common/memmap/memmap.c
@@ -20,21 +20,35 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#include <stdint.h>
 #include <memmap.h>
 
 #ifdef _WIN32
 #define MAP_SHARED    0x01
+
+#ifndef MAP_PRIVATE
 #define MAP_PRIVATE   0x02
+#endif
+
+#ifndef MAP_ANONYMOUS
 #define MAP_ANONYMOUS 0x20
+#endif
+
 #define MAP_ANON      MAP_ANONYMOUS
 #define MAP_FAILED    ((void *) -1)
 #define PROT_READ     0x1
 #define PROT_WRITE    0x2
+
 /* This flag is only available in WinXP+ */
 #ifdef FILE_MAP_EXECUTE
+#ifndef PROT_EXEC
 #define PROT_EXEC     0x4
+#endif
 #else
+#ifndef PROT_EXEC
 #define PROT_EXEC     0x0
+#endif
+
 #define FILE_MAP_EXECUTE 0
 #endif
 
@@ -46,7 +60,7 @@
 # define DWORD_LO(x) (x)
 #endif
 
-void *mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
+void *mmap(void *start, size_t length, int prot, int flags, int fd, size_t offset)
 {
 	uint32_t flProtect, dwDesiredAccess;
 	off_t end;