diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index a8c4ee211c3..24f70373a8a 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1195,7 +1195,7 @@ namespace ts {
 
     // @kind(SyntaxKind.CaseClause)
     export interface CaseClause extends Node {
-        expression?: Expression;
+        expression: Expression;
         statements: NodeArray<Statement>;
     }