diff --git a/stdlib/public/runtime/MetadataLookup.cpp b/stdlib/public/runtime/MetadataLookup.cpp
index 7693994d615..517e44976b7 100644
--- a/stdlib/public/runtime/MetadataLookup.cpp
+++ b/stdlib/public/runtime/MetadataLookup.cpp
@@ -747,8 +747,20 @@ public:
     // Figure out the various levels of generic parameters we have in
     // this type.
     std::vector<unsigned> genericParamCounts;
-    bool innermostIsGeneric =
-      _gatherGenericParameterCounts(typeDecl, genericParamCounts);
+    bool innermostIsGeneric;
+
+    // If we have no parent given, try to form the whole type in one go.
+    if (!parent) {
+      innermostIsGeneric = !genericArgs.empty();
+      if (innermostIsGeneric) {
+        genericParamCounts.push_back(genericArgs.size());
+      }
+    // Otherwise, we'll need to steal the generic arguments from the parent
+    // type to build a nested type.
+    } else {
+      innermostIsGeneric = _gatherGenericParameterCounts(typeDecl,
+                                                         genericParamCounts);
+    }
     bool isGeneric = !genericParamCounts.empty();
 
     // Gather the generic arguments.
diff --git a/test/stdlib/Mirror.swift b/test/stdlib/Mirror.swift
index ff2a4cf0123..1f23fb3f433 100644
--- a/test/stdlib/Mirror.swift
+++ b/test/stdlib/Mirror.swift
@@ -782,4 +782,20 @@ mirrors.test("String.init") {
   expectEqual("42", String(reflecting: 42))
   expectEqual("\"42\"", String(reflecting: "42"))
 }
+
+struct a<b>  {
+    enum c{}
+}
+class d  {}
+struct e<f> {
+    var constraints: [Int: a<f>.c] = [:]
+}
+
+mirrors.test("field with generic nested type") {
+  let x = e<d>()
+  
+  expectTrue(type(of: Mirror(reflecting: x).children.first!.value)
+              == [Int: a<d>.c].self)
+}
+
 runAllTests()