diff --git a/include/tccdefs.h b/include/tccdefs.h
index 5cac7564..ae0364eb 100644
--- a/include/tccdefs.h
+++ b/include/tccdefs.h
@@ -18,8 +18,13 @@
 
 #if __SIZEOF_POINTER__ == 4
     /* 32bit systems. */
+#if defined TARGETOS_OpenBSD
+    #define __SIZE_TYPE__ unsigned long
+    #define __PTRDIFF_TYPE__ long
+#else
     #define __SIZE_TYPE__ unsigned int
     #define __PTRDIFF_TYPE__ int
+#endif
     #define __ILP32__ 1
     #define __INT64_TYPE__ long long
 #elif __SIZEOF_LONG__ == 4