Index: clang/lib/AST/ASTImporter.cpp
===================================================================
--- clang/lib/AST/ASTImporter.cpp
+++ clang/lib/AST/ASTImporter.cpp
@@ -5221,15 +5221,22 @@
   if (Err)
     return std::move(Err);
 
-  // FIXME: Import default argument.
-
   NonTypeTemplateParmDecl *ToD = nullptr;
-  (void)GetImportedOrCreateDecl(
-      ToD, D, Importer.getToContext(),
-      Importer.getToContext().getTranslationUnitDecl(),
-      ToInnerLocStart, ToLocation, D->getDepth(),
-      D->getPosition(), ToDeclName.getAsIdentifierInfo(), ToType,
-      D->isParameterPack(), ToTypeSourceInfo);
+  if (GetImportedOrCreateDecl(ToD, D, Importer.getToContext(),
+                              Importer.getToContext().getTranslationUnitDecl(),
+                              ToInnerLocStart, ToLocation, D->getDepth(),
+                              D->getPosition(),
+                              ToDeclName.getAsIdentifierInfo(), ToType,
+                              D->isParameterPack(), ToTypeSourceInfo))
+    return ToD;
+
+  if (D->hasDefaultArgument()) {
+    ExpectedExpr ToDefaultArgOrErr = import(D->getDefaultArgument());
+    if (!ToDefaultArgOrErr)
+      return ToDefaultArgOrErr.takeError();
+    ToD->setDefaultArgument(*ToDefaultArgOrErr);
+  }
+
   return ToD;
 }
 
Index: clang/unittests/AST/ASTImporterTest.cpp
===================================================================
--- clang/unittests/AST/ASTImporterTest.cpp
+++ clang/unittests/AST/ASTImporterTest.cpp
@@ -901,6 +901,25 @@
           .isValid());
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, NonTypeTemplateParmDeclNoDefaultArg) {
+  Decl *FromTU = getTuDecl("template<int N> struct X {};", Lang_CXX03);
+  auto From = FirstDeclMatcher<NonTypeTemplateParmDecl>().match(
+      FromTU, templateTypeParmDecl(hasName("N")));
+  NonTypeTemplateParmDecl *To = Import(From, Lang_CXX03);
+  ASSERT_FALSE(To->hasDefaultArgument());
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, NonTypeTemplateParmDeclDefaultArg) {
+  Decl *FromTU = getTuDecl("template<int S = 1> struct X {};", Lang_CXX03);
+  auto From = FirstDeclMatcher<NonTypeTemplateParmDecl>().match(
+      FromTU, templateTypeParmDecl(hasName("N")));
+  NonTypeTemplateParmDecl *To = Import(From, Lang_CXX03);
+  ASSERT_TRUE(To->hasDefaultArgument());
+  Expr *ToArg = To->getDefaultArgument();
+  ASSERT_TRUE(isa<IntegerLiteral>(ToArg));
+  ASSERT_EQ(cast<IntegerLiteral>(ToArg)->getValue().getLimitedValue(), 1U);
+}
+
 TEST_P(ASTImporterOptionSpecificTestBase,
        ImportOfTemplatedDeclOfClassTemplateDecl) {
   Decl *FromTU = getTuDecl("template<class X> struct S{};", Lang_CXX03);