Index: clang/include/clang/AST/CommentCommands.td
===================================================================
--- clang/include/clang/AST/CommentCommands.td
+++ clang/include/clang/AST/CommentCommands.td
@@ -139,6 +139,7 @@
 def Pre        : BlockCommand<"pre">;
 def Remark     : BlockCommand<"remark">;
 def Remarks    : BlockCommand<"remarks">;
+def Retval     : BlockCommand<"retval">;
 def Sa         : BlockCommand<"sa">;
 def See        : BlockCommand<"see">;
 def Since      : BlockCommand<"since">;
Index: clang/test/Sema/warn-documentation.cpp
===================================================================
--- clang/test/Sema/warn-documentation.cpp
+++ clang/test/Sema/warn-documentation.cpp
@@ -288,6 +288,11 @@
 /// \param x2 Ccc.
 int test_param22(int x1, int x2, int x3);
 
+// expected-warning@+1 {{empty paragraph passed to '\param' command}}
+/// \param a
+/// \retval 0 Blah blah.
+int test_param23(int a);
+
 //===---
 // Test that we treat typedefs to some non-function types as functions for the
 // purposes of documentation comment parsing.