diff --git a/src/CHANGELOG b/src/CHANGELOG
index 7cdc3f84d..6e82e54f3 100755
--- a/src/CHANGELOG
+++ b/src/CHANGELOG
@@ -75,6 +75,9 @@ ECL 9.11.1:
  - FDEFINITION and SYMBOL-FUNCTION caused an incorrect error condition when
    acting on NIL.
 
+ - CLOS:SET-FUNCALLABLE-INSTANCE-FUNCTION broke the value if SI:INSTANCE-SIG,
+   preventing any further access to the instance slots.
+
 * Sockets:
 
  - The socket option TCP_NODELAY option has been fixed: it was improperly using
diff --git a/src/c/gfun.d b/src/c/gfun.d
index dd9a31e2e..506cfeca5 100644
--- a/src/c/gfun.d
+++ b/src/c/gfun.d
@@ -60,6 +60,8 @@ reshape_instance(cl_object x, int delta)
 {
 	cl_fixnum size = x->instance.length + delta;
 	cl_object aux = ecl_allocate_instance(CLASS_OF(x), size);
+        /* Except for the different size, this must match si_copy_instance */
+        aux->instance.sig = x->instance.sig;
 	memcpy(aux->instance.slots, x->instance.slots,
 	       (delta < 0 ? aux->instance.length : x->instance.length) *
 	       sizeof(cl_object));