diff --git a/git-compat-util.h b/git-compat-util.h
index 105ac28..9863cf6 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -139,6 +139,11 @@
 extern size_t gitstrlcpy(char *, const char *, size_t);
 #endif
 
+#ifdef NO_STRTOUMAX
+#define strtoumax gitstrtoumax
+extern uintmax_t gitstrtoumax(const char *, char **, int);
+#endif
+
 extern void release_pack_memory(size_t);
 
 static inline char* xstrdup(const char *str)