Index: generic/nsf.c
===================================================================
diff -u -ra35803ea84148ebadd79d8527830dcbdebd8873e -r8c16e18f186d305671e9543bf3c5d23fa65dc684
--- generic/nsf.c	(.../nsf.c)	(revision a35803ea84148ebadd79d8527830dcbdebd8873e)
+++ generic/nsf.c	(.../nsf.c)	(revision 8c16e18f186d305671e9543bf3c5d23fa65dc684)
@@ -16904,15 +16904,19 @@
       }
     }
 
-    if (tcd->prefix) {
-      /*
-       * If a prefix was provided, prepend a prefix for the subcommands to
-       * avoid name clashes.
-       */
-      Tcl_Obj *methodName = Tcl_DuplicateObj(tcd->prefix);
-      Tcl_AppendObjToObj(methodName, ov[1]);
-      ov[1] = methodName;
-      INCR_REF_COUNT(ov[1]);
+    /* 
+       If a prefix is provided, it will be prepended to the 2nd argument. This
+       allows for avoiding name clashes if the 2nd argument denotes a
+       subcommand, for example.
+
+       Make sure that the prefix is only prepended, if a second arg is
+       actually available! Otherwise, the requested prefix has no effect.       
+    */
+    if (tcd->prefix && objc > 1) {
+        Tcl_Obj *methodName = Tcl_DuplicateObj(tcd->prefix);
+        Tcl_AppendObjToObj(methodName, ov[1]);
+        ov[1] = methodName;
+        INCR_REF_COUNT(ov[1]);
     }
 
 #if 0
@@ -16926,7 +16930,9 @@
 
     result = CallForwarder(tcd, interp, objc, ov);
 
-    if (tcd->prefix) {DECR_REF_COUNT(ov[1]);}
+    if (tcd->prefix && objc > 1) {
+      DECR_REF_COUNT(ov[1]);
+    }
   exitforwardmethod:
     if (freeList)    {DECR_REF_COUNT2("freeList", freeList);}