diff --git a/compiler/cpp/src/generate/t_cpp_generator.cc b/compiler/cpp/src/generate/t_cpp_generator.cc
index 472644e..2b5057d 100755
--- a/compiler/cpp/src/generate/t_cpp_generator.cc
+++ b/compiler/cpp/src/generate/t_cpp_generator.cc
@@ -3737,10 +3737,17 @@
  * @return Namespaces
  */
 string t_cpp_generator::namespace_prefix(string ns) {
+  // Always start with "::", to avoid possible name collisions with
+  // other names in one of the current namespaces.
+  //
+  // We also need a leading space, in case the name is used inside of a
+  // template parameter.  "MyTemplate<::foo::Bar>" is not valid C++,
+  // since "<:" is an alternative token for "[".
+  string result = " ::";
+
   if (ns.size() == 0) {
-    return "";
+    return result;
   }
-  string result = "";
   string::size_type loc;
   while ((loc = ns.find(".")) != string::npos) {
     result += ns.substr(0, loc);