diff --unified --recursive --text fvwm-2.6.9/fvwm/builtins.c fvwm-patched/fvwm/builtins.c
--- fvwm-2.6.9/fvwm/builtins.c	2020-08-21 16:11:42.983734347 -0600
+++ fvwm-patched/fvwm/builtins.c	2020-08-21 16:12:21.224593859 -0600
@@ -497,6 +497,21 @@
 			if (action)
 				action += next;
 		}
+		else if (!do_add && StrEquals(parm,"buttonwidth"))
+		{
+			int width = 0;
+			int next = 0;
+
+			sscanf(action, "%d%n", &width, &next);
+
+			if (decor->button_width != width)
+			{
+				decor->button_width = width;
+				decor->flags.has_changed = 1;
+			}
+			if (action)
+				action += next;
+		}
 		else if (!do_add && StrEquals(parm,"MinHeight"))
 		{
 			int height = 0;
Only in fvwm-patched/fvwm: builtins.c.orig