diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 69aabcd7d634..0a3e59d55234 100755
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1894,7 +1894,7 @@ private:
     // Ask the template instantiator to do the heavy lifting for us, then adjust
     // the index of the parameter once it's done.
     auto *NewParam =
-        cast_or_null<TemplateParmDecl>(SemaRef.SubstDecl(OldParam, DC, Args));
+        cast<TemplateParmDecl>(SemaRef.SubstDecl(OldParam, DC, Args));
     assert(NewParam->getDepth() == 0 && "unexpected template param depth");
     NewParam->setPosition(NewParam->getPosition() + Depth1IndexAdjustment);
     return NewParam;