diff --git a/cache.h b/cache.h
index 6365381c17..742378f40f 100644
--- a/cache.h
+++ b/cache.h
@@ -142,6 +142,7 @@ extern char *get_graft_file(void);
 
 extern const char **get_pathspec(const char *prefix, char **pathspec);
 extern const char *setup_git_directory(void);
+extern char *prefix_path(const char *prefix, int len, char *path);
 
 #define alloc_nr(x) (((x)+16)*3/2)
 
diff --git a/setup.c b/setup.c
index 1710b16854..b8789de5c5 100644
--- a/setup.c
+++ b/setup.c
@@ -1,6 +1,6 @@
 #include "cache.h"
 
-static char *prefix_path(const char *prefix, int len, char *path)
+char *prefix_path(const char *prefix, int len, char *path)
 {
 	char *orig = path;
 	for (;;) {