diff --git a/src/listfunc.c b/src/listfunc.c
index 8cd6fc5d68..62da1e572b 100644
--- a/src/listfunc.c
+++ b/src/listfunc.c
@@ -267,7 +267,8 @@ Obj             FuncAPPEND_LIST_INTR (
         SET_LEN_STRING(list1, len1 + len2);
         CLEAR_FILTS_LIST(list1);
         // copy data, including terminating zero byte
-        memcpy(CHARS_STRING(list1) + len1, CONST_CHARS_STRING(list2), len2 + 1);
+        // Can't use memcpy, in case list1 == list2
+        SyMemmove(CHARS_STRING(list1) + len1, CONST_CHARS_STRING(list2), len2 + 1);
         return (Obj) 0;
     }
 
diff --git a/tst/testinstall/listindex.tst b/tst/testinstall/listindex.tst
index b5d9f0dd6a..3ce69f27e7 100644
--- a/tst/testinstall/listindex.tst
+++ b/tst/testinstall/listindex.tst
@@ -186,6 +186,20 @@ gap> l := "cheese";; Append(l, [true]); l;
 [ 'c', 'h', 'e', 'e', 's', 'e', true ]
 gap> l := "cheese";; Append(l, []); l;
 "cheese"
+gap> Append(l, l); l;
+"cheesecheese"
+gap> l := "chee";; Append(l, l); l;
+"cheechee"
+gap> l := "cheeseXX";; Append(l, l); l;
+"cheeseXXcheeseXX"
+gap> l := [true];; Append(l, l); l;
+[ true, true ]
+gap> Append(l,l); l;
+[ true, true, true, true ]
+gap> l := [];; Append(l,l); l;
+[  ]
+gap> l := [1,2,3,4];; Append(l,l); l;
+[ 1, 2, 3, 4, 1, 2, 3, 4 ]
 gap> Append(Immutable([1,2,3]), [1,2,3]);
 Error, Append: <list1> must be a mutable list
 gap> Append([1,2,3], () );