Index: generic/tkGrid.c
==================================================================
--- generic/tkGrid.c
+++ generic/tkGrid.c
@@ -1731,16 +1731,18 @@
 
     masterPtr->flags &= ~REQUESTED_RELAYOUT;
 
     /*
      * If the master has no slaves anymore, then don't do anything at all:
-     * just leave the master's size as-is. Otherwise there is no way to
-     * "relinquish" control over the master so another geometry manager can
-     * take over.
+     * just leave the master's size as-is, but signal the master with the
+     * <<GeometryManager>> virtual event.
+     * Otherwise there is no way to "relinquish" control over the master
+     * so another geometry manager can take over.
      */
 
     if (masterPtr->slavePtr == NULL) {
+        TkSendVirtualEvent(masterPtr->tkwin, "GeometryManager", NULL);
 	return;
     }
 
     if (masterPtr->masterDataPtr == NULL) {
 	return;

Index: generic/tkPack.c
==================================================================
--- generic/tkPack.c
+++ generic/tkPack.c
@@ -598,14 +598,18 @@
 
     masterPtr->flags &= ~REQUESTED_REPACK;
 
     /*
      * If the master has no slaves anymore, then don't do anything at all:
-     * just leave the master's size as-is.
+     * just leave the master's size as-is, but signal the master with the
+     * <<GeometryManager>> virtual event.
+     * Otherwise there is no way to "relinquish" control over the master
+     * so another geometry manager can take over.
      */
 
     if (masterPtr->slavePtr == NULL) {
+        TkSendVirtualEvent(masterPtr->tkwin, "GeometryManager", NULL);
 	return;
     }
 
     /*
      * Abort any nested call to ArrangePacking for this window, since we'll do