diff --git a/git-compat-util.h b/git-compat-util.h
index 56212b2..33b68e4 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -70,6 +70,10 @@
 #define PATH_MAX 4096
 #endif
 
+#ifndef PRIuMAX
+#define PRIuMAX "llu"
+#endif
+
 #ifdef __GNUC__
 #define NORETURN __attribute__((__noreturn__))
 #else