diff --git a/diff.c b/diff.c
index 69eb2f76a4..c14f69719b 100644
--- a/diff.c
+++ b/diff.c
@@ -3609,7 +3609,7 @@ static unsigned char *deflate_it(char *data,
 				 unsigned long size,
 				 unsigned long *result_size)
 {
-	int bound;
+	size_t bound;
 	unsigned char *deflated;
 	git_zstream stream;
 	struct repo_config_values *cfg = repo_config_values(the_repository);