--- ./lisp/expand.el.fred	Fri Jan 29 15:12:00 1999
+++ ./lisp/expand.el	Mon Dec 20 07:32:00 1999
@@ -364,8 +364,9 @@
 			  expand-pos (expand-list-to-markers expand-list)
 			  expand-list nil)))
 	      (run-hooks 'expand-expand-hook)
-	      t))))
-  )
+	      t)
+	  nil))
+    nil))
 
 (defun expand-do-expansion ()
   (delete-backward-char (length last-abbrev-text))
--- ./src/abbrev.c.fred	Tue May 18 06:38:03 1999
+++ ./src/abbrev.c	Mon Dec 20 07:30:44 1999
@@ -365,8 +365,15 @@
 
   hook = XSYMBOL (sym)->function;
   if (!NILP (hook))
-    call0 (hook);
-
+    {
+      /* If the expansion is a special one, use the return value from the hook
+	 to know if the expansion happened. */
+      if (!NILP(call0 (hook)) || STRINGP(expansion))
+	return value;
+      else
+	return Qnil;
+    }
+  
   return value;
 }