diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -12168,7 +12168,7 @@
           Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed, P);
       ExprResult R = getDerived().TransformExpr(
           E->getCallOperator()->getParamDecl(I)->getDefaultArg());
-      P->setDefaultArg(R.get());
+      getSema().SetParamDefaultArgument(P, R.get(), R.get()->getBeginLoc());
     }
   }
 
diff --git a/clang/test/SemaTemplate/instantiate-local-class.cpp b/clang/test/SemaTemplate/instantiate-local-class.cpp
--- a/clang/test/SemaTemplate/instantiate-local-class.cpp
+++ b/clang/test/SemaTemplate/instantiate-local-class.cpp
@@ -486,3 +486,14 @@
   }
   void g() { f<int>(); }
 }
+
+namespace PR45000 {
+  template <typename T>
+  void f(int x = [](T x = nullptr) -> int { return x; }());
+  // expected-error@-1 2 {{cannot initialize a parameter of type 'int' with an rvalue of type 'nullptr_t'}}
+  // expected-note@-2 {{in instantiation of default function argument expression for 'operator()<int>'}}
+  // expected-note@-3 2 {{passing argument to parameter 'x' here}}
+
+  void g() { f<int>(); }
+  // expected-note@-1 2 {{in instantiation of default function argument expression for 'f<int>'}}
+}