Index: ChangeLog
===================================================================
diff -u -rc97e67e4e75de882fc249d0b43328c49600ad020 -r986b0a08b5168612ef730a8b575ddbffee9f0b14
--- ChangeLog	(.../ChangeLog)	(revision c97e67e4e75de882fc249d0b43328c49600ad020)
+++ ChangeLog	(.../ChangeLog)	(revision 986b0a08b5168612ef730a8b575ddbffee9f0b14)
@@ -1,3 +1,7 @@
+2012-01-14 <Gustaf.Neumann@wu-wien.ac.at>
+	* xotcl.c Don't overwrite error messages from __unknown handler in
+	several situations (superclass, parameter class, mixin class)
+
 2012-01-12 <Gustaf.Neumann@wu-wien.ac.at>
 	* xotcl.c Backport from nsf: when processing arguments with
 	leading dashes in "configure", accept only method names without
Index: generic/xotcl.c
===================================================================
diff -u -r3e2c28122dff054185286b89f145462fe7e967f2 -r986b0a08b5168612ef730a8b575ddbffee9f0b14
--- generic/xotcl.c	(.../xotcl.c)	(revision 3e2c28122dff054185286b89f145462fe7e967f2)
+++ generic/xotcl.c	(.../xotcl.c)	(revision 986b0a08b5168612ef730a8b575ddbffee9f0b14)
@@ -3307,10 +3307,14 @@
         "' has too many elements.", (char *) NULL);*/
   }
 
-  if (GetXOTclClassFromObj(interp, name, &mixin, 1) != TCL_OK)
-    return XOTclErrBadVal(interp, "mixin", "a class as mixin", ObjStr(name));
+  if (GetXOTclClassFromObj(interp, name, &mixin, 1) != TCL_OK) {
+    char *errorString = ObjStr(Tcl_GetObjResult(interp));
+    if (*errorString == '\0') {
+      XOTclErrBadVal(interp, "mixin", "a class as mixin", ObjStr(name));
+    }
+    return TCL_ERROR;
+  }
 
-
   new = CmdListAdd(mixinList, mixin->object.id, NULL, /*noDuplicates*/ 1);
 
   if (guard) {
@@ -4872,9 +4876,13 @@
   scl = NEW_ARRAY(XOTclClass*, oc);
   for (i = 0; i < oc; i++) {
     if (GetXOTclClassFromObj(interp, ov[i], &scl[i], 1) != TCL_OK) {
+      char *errorString = ObjStr(Tcl_GetObjResult(interp));
       FREE(XOTclClass**, scl);
-      return XOTclErrBadVal(interp, "superclass", "a list of classes",
-                            ObjStr(arg));
+      if (*errorString == '\0') {
+	XOTclErrBadVal(interp, "superclass", "a list of classes",
+		       ObjStr(arg));
+      }
+      return TCL_ERROR;
     }
   }
 
@@ -5204,13 +5212,17 @@
 
   if (opt && opt->parameterClass) pcl = opt->parameterClass;
 
-  if (GetXOTclClassFromObj(interp, pcl,&paramCl, 1) == TCL_OK) {
+  result = GetXOTclClassFromObj(interp, pcl,&paramCl, 1);
+  if (result == TCL_OK) {
     result = XOTclCallMethodWithArgs((ClientData)paramCl, interp,
                                      method, arg, objc-2, objv, flags);
+  } else {
+    char *errorString = ObjStr(Tcl_GetObjResult(interp));
+    if (*errorString == '\0') {
+      XOTclVarErrMsg(interp, "create: can't find parameter class",
+		     (char *) NULL);
+    }
   }
-  else
-    result = XOTclVarErrMsg(interp, "create: can't find parameter class",
-                            (char *) NULL);
   return result;
 }