diff --git a/tests/baselines/reference/classExtendingClassLikeType.errors.txt b/tests/baselines/reference/classExtendingClassLikeType.errors.txt
index 6f9aef927e..5edefd78ec 100644
--- a/tests/baselines/reference/classExtendingClassLikeType.errors.txt
+++ b/tests/baselines/reference/classExtendingClassLikeType.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/classes/classDeclarations/classExtendingClassLikeType.ts(7,18): error TS2304: Cannot find name 'Base'.
+tests/cases/conformance/classes/classDeclarations/classExtendingClassLikeType.ts(7,18): error TS2689: Cannot extend an interface 'Base'. Did you mean 'implements'?
 tests/cases/conformance/classes/classDeclarations/classExtendingClassLikeType.ts(45,18): error TS2508: No base constructor has the specified number of type arguments.
 tests/cases/conformance/classes/classDeclarations/classExtendingClassLikeType.ts(56,18): error TS2510: Base constructors must all have the same return type.
 
@@ -12,7 +12,7 @@ tests/cases/conformance/classes/classDeclarations/classExtendingClassLikeType.ts
     // Error, no Base constructor function
     class D0 extends Base<string, string> {
                      ~~~~
-!!! error TS2304: Cannot find name 'Base'.
+!!! error TS2689: Cannot extend an interface 'Base'. Did you mean 'implements'?
     }
     
     interface BaseConstructor {
diff --git a/tests/baselines/reference/classExtendsEveryObjectType.errors.txt b/tests/baselines/reference/classExtendsEveryObjectType.errors.txt
index 0339dfad13..e1c5137e3a 100644
--- a/tests/baselines/reference/classExtendsEveryObjectType.errors.txt
+++ b/tests/baselines/reference/classExtendsEveryObjectType.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classExtendsEveryObjectType.ts(4,17): error TS2304: Cannot find name 'I'.
+tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classExtendsEveryObjectType.ts(4,17): error TS2689: Cannot extend an interface 'I'. Did you mean 'implements'?
 tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classExtendsEveryObjectType.ts(6,18): error TS2507: Type '{ foo: any; }' is not a constructor function type.
 tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classExtendsEveryObjectType.ts(6,25): error TS2304: Cannot find name 'string'.
 tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classExtendsEveryObjectType.ts(6,31): error TS1005: ',' expected.
@@ -14,7 +14,7 @@ tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/cla
     }
     class C extends I { } // error
                     ~
-!!! error TS2304: Cannot find name 'I'.
+!!! error TS2689: Cannot extend an interface 'I'. Did you mean 'implements'?
     
     class C2 extends { foo: string; } { } // error
                      ~~~~~~~~~~~~~~~~
diff --git a/tests/baselines/reference/classExtendsInterface.errors.txt b/tests/baselines/reference/classExtendsInterface.errors.txt
index 2ecca6cf2c..3714bbb232 100644
--- a/tests/baselines/reference/classExtendsInterface.errors.txt
+++ b/tests/baselines/reference/classExtendsInterface.errors.txt
@@ -1,17 +1,17 @@
-tests/cases/compiler/classExtendsInterface.ts(2,17): error TS2304: Cannot find name 'Comparable'.
-tests/cases/compiler/classExtendsInterface.ts(6,21): error TS2304: Cannot find name 'Comparable2'.
+tests/cases/compiler/classExtendsInterface.ts(2,17): error TS2689: Cannot extend an interface 'Comparable'. Did you mean 'implements'?
+tests/cases/compiler/classExtendsInterface.ts(6,21): error TS2689: Cannot extend an interface 'Comparable2'. Did you mean 'implements'?
 
 
 ==== tests/cases/compiler/classExtendsInterface.ts (2 errors) ====
     interface Comparable {}
     class A extends Comparable {}
                     ~~~~~~~~~~
-!!! error TS2304: Cannot find name 'Comparable'.
+!!! error TS2689: Cannot extend an interface 'Comparable'. Did you mean 'implements'?
     class B implements Comparable {}
      
     interface Comparable2<T> {}
     class A2<T> extends Comparable2<T> {}
                         ~~~~~~~~~~~
-!!! error TS2304: Cannot find name 'Comparable2'.
+!!! error TS2689: Cannot extend an interface 'Comparable2'. Did you mean 'implements'?
     class B2<T> implements Comparable2<T> {}
     
\ No newline at end of file
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
index e590ad42a7..b6767a3b93 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
@@ -13,7 +13,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(18,23): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(18,27): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(18,38): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(20,17): error TS2304: Cannot find name 'I'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(20,17): error TS2689: Cannot extend an interface 'I'. Did you mean 'implements'?
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(23,21): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(29,18): error TS2304: Cannot find name 'M'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(30,24): error TS2314: Generic type 'E<T>' requires 1 type argument(s).
@@ -76,7 +76,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
     
     class D extends I {
                     ~
-!!! error TS2304: Cannot find name 'I'.
+!!! error TS2689: Cannot extend an interface 'I'. Did you mean 'implements'?
     }
     
     interface U extends I {}