diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4346,7 +4346,7 @@
     HasDeducedReturnType = true;
   }
 
-  if (!ArgFunctionType.isNull()) {
+  if (!ArgFunctionType.isNull() && !FunctionType.isNull()) {
     unsigned TDF =
         TDF_TopLevelParameterTypeList | TDF_AllowCompatibleFunctionType;
     // Deduce template arguments from the function type.