diff --git a/src/mred/wxs/wxs_gdi.cxx b/src/mred/wxs/wxs_gdi.cxx
index f1c68147ae..b7aca771ee 100644
--- a/src/mred/wxs/wxs_gdi.cxx
+++ b/src/mred/wxs/wxs_gdi.cxx
@@ -2837,7 +2837,7 @@ static Scheme_Object *os_wxPenSetJoin(int n,  Scheme_Object *p[])
   
   x0 = WITH_VAR_STACK(unbundle_symset_join(p[POFFSET+0], "set-join in pen%"));
 
-  
+  if (!((wxPen *)((Scheme_Class_Object *)THEOBJ)->primdata)->IsMutable()) WITH_VAR_STACK(scheme_signal_error("%s: this %s%% object is locked (in use by a dc<%%> object or in a list of %s constants)", METHODNAME("pen%","set-join"), "pen", "pen"));
   WITH_VAR_STACK(((wxPen *)((Scheme_Class_Object *)p[0])->primdata)->SetJoin(x0));
 
   
@@ -2880,7 +2880,7 @@ static Scheme_Object *os_wxPenSetCap(int n,  Scheme_Object *p[])
   
   x0 = WITH_VAR_STACK(unbundle_symset_cap(p[POFFSET+0], "set-cap in pen%"));
 
-  
+  if (!((wxPen *)((Scheme_Class_Object *)THEOBJ)->primdata)->IsMutable()) WITH_VAR_STACK(scheme_signal_error("%s: this %s%% object is locked (in use by a dc<%%> object or in a list of %s constants)", METHODNAME("pen%","set-cap"), "pen", "pen"));
   WITH_VAR_STACK(((wxPen *)((Scheme_Class_Object *)p[0])->primdata)->SetCap(x0));
 
   
@@ -2923,7 +2923,7 @@ static Scheme_Object *os_wxPenSetWidth(int n,  Scheme_Object *p[])
   
   x0 = WITH_VAR_STACK(objscheme_unbundle_double_in(p[POFFSET+0], 0, 255, "set-width in pen%"));
 
-  
+  if (!((wxPen *)((Scheme_Class_Object *)THEOBJ)->primdata)->IsMutable()) WITH_VAR_STACK(scheme_signal_error("%s: this %s%% object is locked (in use by a dc<%%> object or in a list of %s constants)", METHODNAME("pen%","set-width"), "pen", "pen"));
   WITH_VAR_STACK(((wxPen *)((Scheme_Class_Object *)p[0])->primdata)->SetWidth(x0));
 
   
diff --git a/src/mred/wxs/wxs_gdi.xc b/src/mred/wxs/wxs_gdi.xc
index c8895d8548..3179b43e20 100644
--- a/src/mred/wxs/wxs_gdi.xc
+++ b/src/mred/wxs/wxs_gdi.xc
@@ -178,11 +178,11 @@
 @CREATOR (string,rdouble[0|255],SYM[penStyle]); <> color name
 
 @ "get-width" : double GetWidthF();
-@ "set-width" : void SetWidth(rdouble[0|255]);
+@ "set-width" : void SetWidth(rdouble[0|255]); : : /CHECKMUT[wxPen."pen".METHODNAME("pen%","set-width")]
 @ "get-cap" : SYM[cap] GetCap();
-@ "set-cap" : void SetCap(SYM[cap]);
+@ "set-cap" : void SetCap(SYM[cap]); : : /CHECKMUT[wxPen."pen".METHODNAME("pen%","set-cap")]
 @ "get-join" : SYM[join] GetJoin();
-@ "set-join" : void SetJoin(SYM[join]);
+@ "set-join" : void SetJoin(SYM[join]); : : /CHECKMUT[wxPen."pen".METHODNAME("pen%","set-join")]
 
 @ "get-color" : wxColour! GetColour();
 @ "set-color" : void SetColour(wxColour!);  : : /CHECKMUT[wxPen."pen".METHODNAME("pen%","set-color")] <> color%