Index: generic/nsf.c
===================================================================
diff -u -N -r9797190b64be6005808101d6aff148380c055cb3 -r7e090d5c59743ecf7e8fd8d05d5130c5bce092db
--- generic/nsf.c	(.../nsf.c)	(revision 9797190b64be6005808101d6aff148380c055cb3)
+++ generic/nsf.c	(.../nsf.c)	(revision 7e090d5c59743ecf7e8fd8d05d5130c5bce092db)
@@ -3428,19 +3428,19 @@
   } else if (methodObj->typePtr == Nsf_OT_tclCmdNameType) {
     containsSpace = 0;
   } else {
-    containsSpace = strchr(methodName, ' ') != NULL;
+    containsSpace = NsfHasTclSpace(methodName);
   }
 
   if (containsSpace != 0) {
-    tailContainsSpace = strchr(NSTail(methodName), ' ') != NULL;
+    tailContainsSpace = NsfHasTclSpace(NSTail(methodName));
   } else {
     tailContainsSpace = 0;
   }
   /*fprintf(stderr, "<%s> containsSpace %d tailContainsSpace %d\n", methodName, containsSpace, tailContainsSpace);*/
 
 #if !defined(NDEBUG)
   if (containsSpace != 0) {
-    assert(strchr(methodName, ' ') != 0);
+    assert(NsfHasTclSpace(methodName));
   } else {
     assert(tailContainsSpace == 0);
   }
@@ -16573,6 +16573,11 @@
   nonnull_assert(body != NULL);
 
   nameStr = ObjStr(nameObj);
+
+  if (*nameStr == '\0' || NsfHasTclSpace(nameStr)) {
+    return NsfPrintError(interp, "invalid method name '%s'", nameStr);
+  }
+  
   if (precondition != NULL && postcondition == NULL) {
     return NsfPrintError(interp, "%s method '%s'; when specifying a precondition (%s)"
                          " a postcondition must be specified as well",
Index: generic/nsfInt.h
===================================================================
diff -u -N -r09b4bca7c8d5c44f6be0b2c04ebfcdb7a58fd5ae -r7e090d5c59743ecf7e8fd8d05d5130c5bce092db
--- generic/nsfInt.h	(.../nsfInt.h)	(revision 09b4bca7c8d5c44f6be0b2c04ebfcdb7a58fd5ae)
+++ generic/nsfInt.h	(.../nsfInt.h)	(revision 7e090d5c59743ecf7e8fd8d05d5130c5bce092db)
@@ -1295,4 +1295,11 @@
 #define vsnprintf _vsnprintf
 #endif
 
+/* There are six whitespace characters in Tcl, which serve as element
+   separators in string representations of Tcl lists. See tclUtil.c */
+
+#define NsfHasTclSpace(str) \
+  (strpbrk((str), " \t\n\r\v\f") != NULL)
+
+
 #endif /* _nsf_int_h_ */
Index: tests/methods.test
===================================================================
diff -u -N -r224bb58979f84adf7d1488798a4bfbf84af803ca -r7e090d5c59743ecf7e8fd8d05d5130c5bce092db
--- tests/methods.test	(.../methods.test)	(revision 224bb58979f84adf7d1488798a4bfbf84af803ca)
+++ tests/methods.test	(.../methods.test)	(revision 7e090d5c59743ecf7e8fd8d05d5130c5bce092db)
@@ -4,6 +4,71 @@
 
 ::nx::configure defaultMethodCallProtection false
 
+
+nx::test case name-validity-checks {
+
+  nx::Class create C
+  
+  #
+  # Add some basic tests on valid/invalid method names.
+  #
+
+  ? {set ::h [nsf::method::create ::C "" {} {;}]} "invalid method name ''"
+  ? {set ::h [nsf::method::create ::C {e1 m1} {} {;}]} "invalid method name 'e1 m1'"
+  ? {set ::h [nsf::method::create ::C "e1\tm1" {} {;}]} "invalid method name 'e1\tm1'"
+  ? {set ::h [nsf::method::create ::C {{e1 m1}} {} {;}]} "invalid method name '{e1 m1}'"
+  ? {set ::h [nsf::method::create ::C ":" {} {;}]} {can't create procedure ":" in non-global namespace with name starting with ":"}
+  
+  # These are Tcl whitespace characters, which act as the separators in
+  # Tcl list string reps:
+  #
+  # \u0009  \t      TAB
+  # \u000A  \n      NEWLINE
+  # \u000B  \v      VERTICAL TAB
+  # \u000C  \f      FORM FEED
+  # \u000D  \r      CARRIAGE RETURN
+  # \u0020          SPACE
+  #
+  
+  ? {set ::h [nsf::method::create ::C "  e1   " {} {;}]} "invalid method name '  e1   '"
+  ? {set ::h [nsf::method::create ::C {"  e1   "} {} {;}]} {invalid method name '"  e1   "'}
+  
+  ? {set ::h [nsf::method::create ::C "\te1" {} {;}]} "invalid method name '\te1'"
+  ? {set ::h [nsf::method::create ::C "e1\tm1" {} {;}]} "invalid method name 'e1\tm1'"
+  
+  ? {set ::h [nsf::method::create ::C "\ne1" {} {;}]} "invalid method name '\ne1'"
+  ? {set ::h [nsf::method::create ::C "e1\nm1" {} {;}]} "invalid method name 'e1\nm1'"
+  
+  ? {set ::h [nsf::method::create ::C "\ve1" {} {;}]} "invalid method name '\ve1'"
+  ? {set ::h [nsf::method::create ::C "e1\vm1" {} {;}]} "invalid method name 'e1\vm1'"
+  
+  ? {set ::h [nsf::method::create ::C "\fe1" {} {;}]} "invalid method name '\fe1'"
+  ? {set ::h [nsf::method::create ::C "e1\fm1" {} {;}]} "invalid method name 'e1\fm1'"
+  
+  ? {set ::h [nsf::method::create ::C "\re1" {} {;}]} "invalid method name '\re1'"
+  ? {set ::h [nsf::method::create ::C "e1\rm1" {} {;}]} "invalid method name 'e1\rm1'"
+  
+  
+  # There is no tangible difference between a bareword and a one-element
+  # list in Tcl (singelton list). So, there will remain exotique method
+  # names including curly braces, along with other peculiar names,
+  # e.g. those starting with #.
+  ? {set ::h [nsf::method::create ::C {{{{{a}}}}} {} {;}]} {::nsf::classes::C::{{{{a}}}}};
+  ? {set ::h [nsf::method::create ::C {#a} {} {;}]} {::nsf::classes::C::#a};
+    
+  #
+  # In Tcl, the empty string is a valid command (proc) name, with
+  # obscure effects (e.g., cannot be renamed, unless) . We disallow it as method name.
+  #
+    
+  ? {set ::h [nsf::method::create ::C "" {} {;}]} "invalid method name ''"
+    
+  # But, we can safeguard against list elements containing Tcl
+  # whitespace characters at any nesting level.
+  ? {set ::h [nsf::method::create ::C {{{{{a b}}}}} {} {;}]} {invalid method name '{{{{a b}}}}'}; 
+}
+    
+    
 nx::test configure -count 10
 
 nx::Class create C {