Index: include/clang/Basic/DiagnosticCommentKinds.td
===================================================================
--- include/clang/Basic/DiagnosticCommentKinds.td	(revision 181480)
+++ include/clang/Basic/DiagnosticCommentKinds.td	(working copy)
@@ -157,7 +157,8 @@
   InGroup<Documentation>, DefaultIgnore;
 
 def warn_unknown_comment_command_name : Warning<
-  "unknown command tag name">, InGroup<Documentation>, DefaultIgnore;
+  "unknown command tag name">,
+  InGroup<DocumentationUnknownCommand>, DefaultIgnore;
 
 def warn_correct_comment_command_name : Warning<
   "unknown command tag name '%0'; did you mean '%1'?">,
Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td	(revision 181480)
+++ include/clang/Basic/DiagnosticGroups.td	(working copy)
@@ -68,7 +68,9 @@
 def : DiagGroup<"div-by-zero">;
 
 def DocumentationHTML : DiagGroup<"documentation-html">;
-def DocumentationPedantic : DiagGroup<"documentation-pedantic">;
+def DocumentationUnknownCommand : DiagGroup<"documentation-unknown-command">;
+def DocumentationPedantic : DiagGroup<"documentation-pedantic",
+                                      [DocumentationUnknownCommand]>;
 def DocumentationDeprecatedSync : DiagGroup<"documentation-deprecated-sync">;
 def Documentation : DiagGroup<"documentation",
                               [DocumentationHTML,