diff --git a/clang-tools-extra/pseudo/lib/cxx/CXX.cpp b/clang-tools-extra/pseudo/lib/cxx/CXX.cpp
--- a/clang-tools-extra/pseudo/lib/cxx/CXX.cpp
+++ b/clang-tools-extra/pseudo/lib/cxx/CXX.cpp
@@ -162,6 +162,10 @@
   return symbolToToken(P.Lookahead) != tok::kw_else;
 }
 
+bool guardNextTokenNotColCol(const GuardParams &P) {
+  return symbolToToken(P.Lookahead) != tok::coloncolon;
+}
+
 // Whether this e.g. decl-specifier contains an "exclusive" type such as a class
 // name, and thus can't combine with a second exclusive type.
 //
@@ -308,6 +312,16 @@
            selection_statement_0if_1constexpr_2l_paren_3condition_4r_paren_5statement,
        guardNextTokenNotElse},
 
+      {(RuleID)Rule::simple_type_specifier_0nested_name_specifier_1type_name,
+       guardNextTokenNotColCol},
+      {(RuleID)Rule::simple_type_specifier_0nested_name_specifier_1template_name,
+       guardNextTokenNotColCol},
+      {(RuleID)Rule::simple_type_specifier_0type_name,
+       guardNextTokenNotColCol},
+      {(RuleID)Rule::simple_type_specifier_0template_name,
+       guardNextTokenNotColCol
+      },
+
       // The grammar distinguishes (only) user-defined vs plain string literals,
       // where the clang lexer distinguishes (only) encoding types.
       {(RuleID)Rule::user_defined_string_literal_chunk_0string_literal,
diff --git a/clang-tools-extra/pseudo/lib/cxx/cxx.bnf b/clang-tools-extra/pseudo/lib/cxx/cxx.bnf
--- a/clang-tools-extra/pseudo/lib/cxx/cxx.bnf
+++ b/clang-tools-extra/pseudo/lib/cxx/cxx.bnf
@@ -370,11 +370,11 @@
 defining-type-specifier := enum-specifier
 defining-type-specifier-seq := defining-type-specifier
 defining-type-specifier-seq := defining-type-specifier defining-type-specifier-seq [guard]
-simple-type-specifier := nested-name-specifier_opt type-name
+simple-type-specifier := nested-name-specifier_opt type-name [guard]
 simple-type-specifier := nested-name-specifier TEMPLATE simple-template-id
 simple-type-specifier := decltype-specifier
 simple-type-specifier := placeholder-type-specifier
-simple-type-specifier := nested-name-specifier_opt template-name
+simple-type-specifier := nested-name-specifier_opt template-name [guard]
 simple-type-specifier := builtin-type
 builtin-type := CHAR
 builtin-type := CHAR8_T