diff --git a/cache.h b/cache.h
index 4d014541ab..260e4ee44a 100644
--- a/cache.h
+++ b/cache.h
@@ -703,7 +703,7 @@ extern int unmerged_index(const struct index_state *);
  * provided, the space-separated list of files that differ will be appended
  * to it.
  */
-extern int index_has_changes(const struct index_state *istate,
+extern int index_has_changes(struct index_state *istate,
 			     struct tree *tree,
 			     struct strbuf *sb);
 
diff --git a/read-cache.c b/read-cache.c
index 7b1354d759..86134e56a6 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2122,7 +2122,7 @@ int unmerged_index(const struct index_state *istate)
 	return 0;
 }
 
-int index_has_changes(const struct index_state *istate,
+int index_has_changes(struct index_state *istate,
 		      struct tree *tree,
 		      struct strbuf *sb)
 {