diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -2892,7 +2892,7 @@
       unsigned i = PV->getFunctionScopeIndex();
       // This parameter might be from a freestanding function type within the
       // function and isn't necessarily referring to one of FD's parameters.
-      if (FD->getParamDecl(i) == PV)
+      if (i < FD->getNumParams() && FD->getParamDecl(i) == PV)
         return FD->getCanonicalDecl()->getParamDecl(i);
     }
   }
diff --git a/clang/test/SemaCXX/PR38077.cpp b/clang/test/SemaCXX/PR38077.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/PR38077.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify %s
+
+// expected-no-diagnostics
+
+int f1( unsigned ) { return 0; }
+
+template <class R, class... Args>
+struct S1 {
+    S1( R(*f)(Args...) ) {}
+};
+
+int main() {
+    S1 s1( f1 );
+}