diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2350,6 +2350,15 @@
       ParmVarDecl *OldParam, MultiLevelTemplateArgumentList &Args,
       llvm::SmallVectorImpl<TypedefNameDecl *> &MaterializedTypedefs) {
     TypeSourceInfo *OldDI = OldParam->getTypeSourceInfo();
+
+    if (auto *OldTypedefT = OldParam->getType()->getAs<TypedefType>()) {
+      TypedefNameDecl *OldTypedefDecl = OldTypedefT->getDecl();
+      auto *CD = cast<CXXConstructorDecl>(OldParam->getDeclContext());
+      // If the typedef is not a local typedef, then skip the transform.
+      if (OldTypedefDecl->getDeclContext() != CD->getDeclContext())
+        return OldParam;
+    }
+
     TypeSourceInfo *NewDI;
     if (auto PackTL = OldDI->getTypeLoc().getAs<PackExpansionTypeLoc>()) {
       // Expand out the one and only element in each inner pack.
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -5865,6 +5865,56 @@
   EXPECT_EQ(Record, CompletedTags.front());
 }
 
+// FIXME Move these tests out of ASTImporterTest. For that we need to factor
+// out the ASTImporter specific pars from ASTImporterOptionSpecificTestBase
+// into a new test Fixture. Then we should lift up this Fixture to its own
+// implementation file and only then could we reuse the Fixture in other AST
+// unitttests.
+struct CTAD : ASTImporterOptionSpecificTestBase {};
+
+TEST_P(CTAD, DeductionGuideShouldReferToANonLocalTypedef) {
+  Decl *TU = getTuDecl(
+      R"(
+      typedef int U;
+      template <typename T> struct A {
+        A(U, T);
+      };
+      A a{(int)0, (int)0};
+      )",
+      Lang_CXX17, "input.cc");
+  TU->dump();
+  auto *Guide = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+      TU, cxxDeductionGuideDecl());
+  auto *Typedef = FirstDeclMatcher<TypedefNameDecl>().match(
+      TU, typedefNameDecl(hasName("U")));
+  ParmVarDecl *Param = Guide->getParamDecl(0);
+  // The type of the first param (which is a typedef) should match the typedef
+  // in the global scope.
+  EXPECT_EQ(Param->getType()->getAs<TypedefType>()->getDecl(), Typedef);
+}
+
+TEST_P(CTAD, DeductionGuideShouldCopyALocalTypedef) {
+  Decl *TU = getTuDecl(
+      R"(
+      template <typename T> struct A {
+        typedef T U;
+        A(U, T);
+      };
+      A a{(int)0, (int)0};
+      )",
+      Lang_CXX17, "input.cc");
+  TU->dump();
+  auto *Guide = FirstDeclMatcher<CXXDeductionGuideDecl>().match(
+      TU, cxxDeductionGuideDecl());
+  auto *Typedef = FirstDeclMatcher<TypedefNameDecl>().match(
+      TU, typedefNameDecl(hasName("U")));
+  ParmVarDecl *Param = Guide->getParamDecl(0);
+  EXPECT_NE(Param->getType()->getAs<TypedefType>()->getDecl(), Typedef);
+}
+
+INSTANTIATE_TEST_CASE_P(ParameterizedTests, CTAD,
+                        DefaultTestValuesForRunOptions, );
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ASTImporterLookupTableTest,
                         DefaultTestValuesForRunOptions, );