diff --git a/lrzip_private.h b/lrzip_private.h
index d43fd3c..c3857cc 100644
--- a/lrzip_private.h
+++ b/lrzip_private.h
@@ -234,7 +234,7 @@ typedef sem_t cksem_t;
 
 #define NO_MD5		(!(HASH_CHECK) && !(HAS_MD5))
 
-#define BITS32		(sizeof(long) == 4)
+#define BITS32		(sizeof(void*) == 4)
 
 #define CTYPE_NONE 3
 #define CTYPE_BZIP2 4