diff --git a/lib/ClangImporter/ClangImporter.cpp b/lib/ClangImporter/ClangImporter.cpp
index 3d7841a0b7037..c093cd8ffa73b 100644
--- a/lib/ClangImporter/ClangImporter.cpp
+++ b/lib/ClangImporter/ClangImporter.cpp
@@ -2742,6 +2742,15 @@ getClangOwningModule(ClangNode Node, const clang::ASTContext &ClangCtx) {
         originalDecl = pattern;
       }
     }
+    if (!originalDecl->hasOwningModule()) {
+      if (auto cxxRecordDecl = dyn_cast<clang::CXXRecordDecl>(D)) {
+        if (auto pattern = cxxRecordDecl->getTemplateInstantiationPattern()) {
+          // Class template instantiations sometimes don't have an owning Clang
+          // module, if the instantiation is not typedef-ed.
+          originalDecl = pattern;
+        }
+      }
+    }
 
     return ExtSource->getModule(originalDecl->getOwningModuleID());
   }
diff --git a/lib/ClangImporter/ImportDecl.cpp b/lib/ClangImporter/ImportDecl.cpp
index 25f2fb25f6cfc..d36706bc3b98b 100644
--- a/lib/ClangImporter/ImportDecl.cpp
+++ b/lib/ClangImporter/ImportDecl.cpp
@@ -2793,7 +2793,7 @@ namespace {
 
       // If this module is declared as a C++ module, try to synthesize
       // conformances to Swift protocols from the Cxx module.
-      auto clangModule = decl->getOwningModule();
+      auto clangModule = Impl.getClangOwningModule(result->getClangNode());
       if (clangModule && requiresCPlusPlus(clangModule)) {
         auto nominalDecl = cast<NominalTypeDecl>(result);
         conformToCxxIteratorIfNeeded(Impl, nominalDecl, decl);
diff --git a/test/Interop/Cxx/stdlib/Inputs/std-vector.h b/test/Interop/Cxx/stdlib/Inputs/std-vector.h
index 319ff52279429..f7c375ad854ff 100644
--- a/test/Interop/Cxx/stdlib/Inputs/std-vector.h
+++ b/test/Interop/Cxx/stdlib/Inputs/std-vector.h
@@ -2,8 +2,10 @@
 #define TEST_INTEROP_CXX_STDLIB_INPUTS_STD_VECTOR_H
 
 #include <vector>
+#include <string>
 
 using Vector = std::vector<int>;
+using VectorOfString = std::vector<std::string>;
 
 inline Vector initVector() { return {}; }
 
diff --git a/test/Interop/Cxx/stdlib/use-std-vector.swift b/test/Interop/Cxx/stdlib/use-std-vector.swift
index 347c6f335feac..80d2ee31bd9cb 100644
--- a/test/Interop/Cxx/stdlib/use-std-vector.swift
+++ b/test/Interop/Cxx/stdlib/use-std-vector.swift
@@ -12,13 +12,13 @@ import CxxStdlib.vector
 
 var StdVectorTestSuite = TestSuite("StdVector")
 
-StdVectorTestSuite.test("init") {
+StdVectorTestSuite.test("VectorOfInt.init") {
     let v = Vector()
     expectEqual(v.size(), 0)
     expectTrue(v.empty())
 }
 
-StdVectorTestSuite.test("push back") {
+StdVectorTestSuite.test("VectorOfInt.push_back") {
     var v = Vector()
     let _42: CInt = 42
     v.push_back(_42)
@@ -33,7 +33,7 @@ func fill(vector v: inout Vector) {
     v.push_back(CInt(3))
 }
 
-StdVectorTestSuite.test("for loop") {
+StdVectorTestSuite.test("VectorOfInt for loop") {
     var v = Vector()
     fill(vector: &v)
 
@@ -45,7 +45,23 @@ StdVectorTestSuite.test("for loop") {
     expectEqual(count, 4)
 }
 
-StdVectorTestSuite.test("map") {
+StdVectorTestSuite.test("VectorOfString for loop") {
+    var v = VectorOfString()
+    var count = 0
+    for _ in v {
+        count += 1
+    }
+    expectEqual(count, 0)
+
+    v.push_back(std.string("abc"))
+    v.push_back(std.string("ab"))
+    for it in v {
+        count += it.length()
+    }
+    expectEqual(count, 5)
+}
+
+StdVectorTestSuite.test("VectorOfInt.map") {
     var v = Vector()
     fill(vector: &v)
 
@@ -53,4 +69,14 @@ StdVectorTestSuite.test("map") {
     expectEqual(a, [6, 7, 8])
 }
 
+StdVectorTestSuite.test("VectorOfString.map") {
+    var v = VectorOfString()
+    v.push_back(std.string("abc"))
+    v.push_back(std.string("a"))
+    v.push_back(std.string("ab"))
+
+    let a = v.map { $0.length() }
+    expectEqual(a, [3, 1, 2])
+}
+
 runAllTests()