diff --git a/lib/Serialization/Deserialization.cpp b/lib/Serialization/Deserialization.cpp
index 4c62bb3728b1a..8e9d098532b23 100644
--- a/lib/Serialization/Deserialization.cpp
+++ b/lib/Serialization/Deserialization.cpp
@@ -1468,6 +1468,10 @@ ModuleFile::resolveCrossReference(ModuleID MID, uint32_t pathLen) {
             if (auto overlayModule = LF->getOverlayModule()) {
               nestedType = findNestedTypeDeclInModule(getFile(), overlayModule,
                                                       memberName, baseType);
+            } else if (LF->getParentModule() != extensionModule) {
+              nestedType = findNestedTypeDeclInModule(getFile(),
+                                                      LF->getParentModule(),
+                                                      memberName, baseType);
             }
           }
         }
diff --git a/test/Serialization/multi-file-nested-type-extension.swift b/test/Serialization/multi-file-nested-type-extension.swift
index fd2d139a25009..181fc38b72c52 100644
--- a/test/Serialization/multi-file-nested-type-extension.swift
+++ b/test/Serialization/multi-file-nested-type-extension.swift
@@ -10,7 +10,7 @@
 // REQUIRES: asserts
 
 // CHECK: Statistics
-// CHECK: 1 Serialization - # of nested types resolved without full lookup
+// CHECK: 2 Serialization - # of nested types resolved without full lookup
 
 // Note the Optional here and below; this was once necessary to produce a crash.
 // Without it, the type of the parameter is initialized "early" enough to not
@@ -21,3 +21,9 @@ extension Outer {
 
   public func useTypes(_: Outer.Callback?) {}
 }
+
+extension OuterClass.Inner {
+  public static var instance: OuterClass.Inner {
+    return OuterClass.Inner()
+  }
+}