diff --git a/lib/IRGen/IRGenDebugInfo.cpp b/lib/IRGen/IRGenDebugInfo.cpp
index e8b4f279d1cd7..8f31a88b29713 100644
--- a/lib/IRGen/IRGenDebugInfo.cpp
+++ b/lib/IRGen/IRGenDebugInfo.cpp
@@ -729,6 +729,16 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
     if (!DC)
       return TheCU;
 
+    auto createContext = [&](NominalTypeDecl &NTD) {
+      GenericContextScope scope(
+          IGM, NTD.getGenericSignature().getCanonicalSignature());
+
+      auto Ty = NTD.getDeclaredInterfaceType();
+      // Create a Forward-declared type.
+      auto DbgTy = DebugTypeInfo::getForwardDecl(Ty);
+      return getOrCreateType(DbgTy);
+    };
+
     if (isa<FuncDecl>(DC))
       if (auto *Decl = IGM.getSILModule().lookUpFunction(SILDeclRef(
               cast<AbstractFunctionDecl>(DC), SILDeclRef::Kind::Func)))
@@ -742,7 +752,6 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
 
     // We don't model these in DWARF.
     case DeclContextKind::Initializer:
-    case DeclContextKind::ExtensionDecl:
     case DeclContextKind::SubscriptDecl:
     case DeclContextKind::EnumElementDecl:
     case DeclContextKind::TopLevelCodeDecl:
@@ -761,16 +770,17 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
       return getOrCreateContext(DC->getParent());
     case DeclContextKind::MacroDecl:
       return getOrCreateContext(DC->getParent());
+    case DeclContextKind::ExtensionDecl: {
+      auto *ED = cast<ExtensionDecl>(DC);
+      if (auto *NTD = ED->getExtendedNominal())
+        return createContext(*NTD);
+      return getOrCreateContext(DC->getParent());
+    }
     case DeclContextKind::GenericTypeDecl: {
-      // The generic signature of this nominal type has no relation to the current
-      // function's generic signature.
+      // The generic signature of this nominal type has no relation to the
+      // current function's generic signature.
       auto *NTD = cast<NominalTypeDecl>(DC);
-      GenericContextScope scope(IGM, NTD->getGenericSignature().getCanonicalSignature());
-
-      auto Ty = NTD->getDeclaredInterfaceType();
-      // Create a Forward-declared type.
-      auto DbgTy = DebugTypeInfo::getForwardDecl(Ty);
-      return getOrCreateType(DbgTy);
+      return createContext(*NTD);
     }
     }
     return TheCU;
diff --git a/test/DebugInfo/Errors.swift b/test/DebugInfo/Errors.swift
index 41f5b31e732ac..9dc1f3b715d67 100644
--- a/test/DebugInfo/Errors.swift
+++ b/test/DebugInfo/Errors.swift
@@ -3,7 +3,7 @@ public enum E : Error { case Err }
 
 // Function throws.
 public func throwError() throws { throw E.Err }
-// CHECK: !DISubprogram(name: "throwError", {{.*}}thrownTypes: ![[THROWN:.*]])
+// CHECK-DAG: !DISubprogram(name: "throwError", {{.*}}thrownTypes: ![[THROWN:.*]])
 // CHECK-DAG: ![[THROWN]] = !{![[ERROR:[0-9]+]]}
 // CHECK-DAG: ![[ERROR]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Error"
 
diff --git a/test/DebugInfo/NestedTypes.swift b/test/DebugInfo/NestedTypes.swift
index eb4c82a85394e..de0ef99c4a077 100644
--- a/test/DebugInfo/NestedTypes.swift
+++ b/test/DebugInfo/NestedTypes.swift
@@ -16,3 +16,19 @@ public let e : Enum = .WithClass(C())
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "WithStruct",
 // CHECK-SAME:           size: 128)
 
+public struct D<U> {
+  var v : V
+  let u: U
+}
+
+extension D {
+  struct V {
+    internal var obj: Int
+  }
+}
+
+public let d = D<Int>(v: D.V(obj: 1), u: 2)
+
+// CHECK: ![[D:.*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "D"
+// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "V", scope: ![[D]],
+
diff --git a/test/DebugInfo/typealias.swift b/test/DebugInfo/typealias.swift
index 993cf2fa14e76..7942c96cbd20f 100644
--- a/test/DebugInfo/typealias.swift
+++ b/test/DebugInfo/typealias.swift
@@ -120,10 +120,11 @@ public protocol Down {
 }
 
 public typealias DependentAlias<T : Up> = T.A.A
+// CHECK-DAG: ![[DEPENDENTALIAS:.*]] = !DIDerivedType(tag: DW_TAG_typedef, name: "DependentAlias", {{.*}} baseType: ![[INTTYPE]])
 
 extension Up where A.A == Int {
   public func foo() {
-    // CHECK-DAG: !DILocalVariable(name: "gg",{{.*}} type: ![[INTTYPE]]
+    // CHECK-DAG: !DILocalVariable(name: "gg",{{.*}} type: ![[DEPENDENTALIAS]]
     var gg: DependentAlias<Self> = 123
   }
 }