Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -3175,7 +3175,11 @@
     //   declared] with the same access [as the template].
     if (auto *DG = dyn_cast<CXXDeductionGuideDecl>(NonTemplateMember)) {
       auto *TD = DG->getDeducedTemplate();
-      if (AS != TD->getAccess()) {
+      // Access specifiers are only meaningful if both the template and the
+      // deduction guide are from the same scope.
+      if (AS != TD->getAccess() &&
+          TD->getDeclContext()->getRedeclContext()->Equals(
+              DG->getDeclContext()->getRedeclContext())) {
         Diag(DG->getBeginLoc(), diag::err_deduction_guide_wrong_access);
         Diag(TD->getBeginLoc(), diag::note_deduction_guide_template_access)
             << TD->getAccess();
Index: test/Sema/crash-deduction-guide-access.cpp
===================================================================
--- test/Sema/crash-deduction-guide-access.cpp
+++ test/Sema/crash-deduction-guide-access.cpp
@@ -0,0 +1,11 @@
+// RUN: not %clang_cc1 -x c++ -std=c++17 -fsyntax-only %s
+template <typename U>
+class Imp {
+  template <typename F>
+  explicit Imp(F f);
+};
+
+template <typename T>
+class Cls {
+  explicit Imp() : f() {}
+};