diff --git a/lib/IRGen/GenArchetype.cpp b/lib/IRGen/GenArchetype.cpp
index a74471d787b2a..9b04b4e87dfad 100644
--- a/lib/IRGen/GenArchetype.cpp
+++ b/lib/IRGen/GenArchetype.cpp
@@ -99,7 +99,7 @@ class OpaqueArchetypeTypeInfo
   void collectMetadataForOutlining(OutliningMetadataCollector &collector,
                                    SILType T) const override {
     // We'll need formal type metadata for this archetype.
-    collector.collectFormalTypeMetadata(T.getSwiftRValueType());
+    collector.collectTypeMetadataForLayout(T);
   }
 };
 
diff --git a/lib/IRGen/Outlining.cpp b/lib/IRGen/Outlining.cpp
index cae28be03c47a..c4c60dc6ed573 100644
--- a/lib/IRGen/Outlining.cpp
+++ b/lib/IRGen/Outlining.cpp
@@ -35,10 +35,14 @@ void OutliningMetadataCollector::collectTypeMetadataForLayout(SILType type) {
     return;
   }
 
+  CanType formalType = type.getSwiftRValueType();
+  if (isa<FixedTypeInfo>(IGF.IGM.getTypeInfoForLowered(formalType))) {
+    return;
+  }
+
   // If the type is a legal formal type, add it as a formal type.
   // FIXME: does this force us to emit a more expensive metadata than we need
   // to?
-  CanType formalType = type.getSwiftRValueType();
   if (formalType->isLegalFormalType()) {
     return collectFormalTypeMetadata(formalType);
   }
@@ -53,9 +57,7 @@ void OutliningMetadataCollector::collectTypeMetadataForLayout(SILType type) {
 
 void OutliningMetadataCollector::collectFormalTypeMetadata(CanType type) {
   // If the type has no archetypes, we can emit it from scratch in the callee.
-  if (!type->hasArchetype()) {
-    return;
-  }
+  assert(type->hasArchetype());
 
   auto key = LocalTypeDataKey(type, LocalTypeDataKind::forFormalTypeMetadata());
   if (Values.count(key)) return;
diff --git a/test/IRGen/outlined_copy_addr.swift b/test/IRGen/outlined_copy_addr.swift
index a4973b40cc1a4..b68a57b5bab25 100644
--- a/test/IRGen/outlined_copy_addr.swift
+++ b/test/IRGen/outlined_copy_addr.swift
@@ -18,9 +18,33 @@ public struct StructWithBaseStruct<T: BaseProt> {
     var elem2: BaseStruct<Element>
 }
 
-// CHECK-LABEL: define hidden swiftcc void @"$S11outcopyaddr010StructWithbc4BaseB0V4elemAA0bcdB0VyxGvg"(%T11outcopyaddr014StructWithBaseB0V.0* noalias nocapture sret, %swift.type* %"StructWithStructWithBaseStruct<T>", %T11outcopyaddr010StructWithbc4BaseB0V* noalias nocapture swiftself)
-// CHECK: call %T11outcopyaddr014StructWithBaseB0V.0* @"$S11outcopyaddr014StructWithBaseB0VyxGAA9ChildProtRzlWOc"
+// CHECK-LABEL: define hidden swiftcc void @"$S11outcopyaddr010StructWithbc4BaseB0V4elemAA0bcdB0VyxGvg"(%T11outcopyaddr014StructWithBaseB0V.4* noalias nocapture sret, %swift.type* %"StructWithStructWithBaseStruct<T>", %T11outcopyaddr010StructWithbc4BaseB0V* noalias nocapture swiftself)
+// CHECK: call %T11outcopyaddr014StructWithBaseB0V.4* @"$S11outcopyaddr014StructWithBaseB0VyxGAA9ChildProtRzlWOc"
 public struct StructWithStructWithBaseStruct<T: ChildProt> {
     public typealias Element = T
     let elem: StructWithBaseStruct<Element>
 }
+
+protocol P { }
+
+class OtherPrivate<T> { }
+
+struct OtherInternal<T> {
+  var myPrivate: OtherPrivate<T>? = nil
+}
+
+struct MyPrivate<T: P> {
+  var otherHelper: OtherInternal<T>? = nil
+
+  // CHECK-LABEL: define hidden swiftcc {{i32|i64}} @"$S11outcopyaddr9MyPrivateVyACyxGxcfC"(%swift.opaque* noalias nocapture, %swift.type* %T, i8** %T.P) {{.*}} {
+  // CHECK: call %T11outcopyaddr9MyPrivateV* @"$S11outcopyaddr9MyPrivateVyxGAA1PRzlWOh"(%T11outcopyaddr9MyPrivateV* %self)
+  // CHECK: ret
+  init(_: T) { }
+}
+
+extension P {
+  func foo(data: Any) {
+    _ = MyPrivate(data as! Self)
+  }
+}
+
diff --git a/test/multifile/Inputs/outlined-thunks-other.swift b/test/multifile/Inputs/outlined-thunks-other.swift
new file mode 100644
index 0000000000000..95da4035497e4
--- /dev/null
+++ b/test/multifile/Inputs/outlined-thunks-other.swift
@@ -0,0 +1,5 @@
+private class OtherPrivate<T> { }
+
+struct OtherInternal<T> {
+  fileprivate var myPrivate: OtherPrivate<T>? = nil
+}
diff --git a/test/multifile/outlined-thunks.swift b/test/multifile/outlined-thunks.swift
new file mode 100644
index 0000000000000..b24a959ca7b81
--- /dev/null
+++ b/test/multifile/outlined-thunks.swift
@@ -0,0 +1,18 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -emit-library -module-name outlined_thunks %S/Inputs/outlined-thunks-other.swift %s
+// RUN: %target-build-swift -emit-library -module-name outlined_thunks -whole-module-optimization %S/Inputs/outlined-thunks-other.swift %s
+
+// rdar://problem/39470607
+
+protocol P { }
+
+private struct MyPrivate<T: P> {
+  private var otherHelper: OtherInternal<T>? = nil
+  init(_: T) { }
+}
+
+extension P {
+  func foo(data: Any) {
+    _ = MyPrivate(data as! Self)
+  }
+}