diff --git a/sql/key.cc b/sql/key.cc
index 31b65adabe9..77660c0fc8c 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -176,7 +176,7 @@ void key_copy(uchar *to_key, uchar *from_record, KEY *key_info,
   @param key_length  specifies length of all keyparts that will be restored
 */
 
-void key_restore(uchar *to_record, uchar *from_key, KEY *key_info,
+void key_restore(uchar *to_record, const uchar *from_key, KEY *key_info,
                  uint key_length)
 {
   uint length;
diff --git a/sql/key.h b/sql/key.h
index 47b981f5298..f2521e4a665 100644
--- a/sql/key.h
+++ b/sql/key.h
@@ -29,7 +29,7 @@ int find_ref_key(KEY *key, uint key_count, uchar *record, Field *field,
                  uint *key_length, uint *keypart);
 void key_copy(uchar *to_key, uchar *from_record, KEY *key_info, uint key_length,
               bool with_zerofill= FALSE);
-void key_restore(uchar *to_record, uchar *from_key, KEY *key_info,
+void key_restore(uchar *to_record, const uchar *from_key, KEY *key_info,
                  uint key_length);
 bool key_cmp_if_same(TABLE *form,const uchar *key,uint index,uint key_length);
 void key_unpack(String *to, TABLE *table, KEY *key);