diff --git a/test/com/google/javascript/jscomp/CompilerTestCase.java b/test/com/google/javascript/jscomp/CompilerTestCase.java
index a5f8229f96e..f459bbbbef4 100644
--- a/test/com/google/javascript/jscomp/CompilerTestCase.java
+++ b/test/com/google/javascript/jscomp/CompilerTestCase.java
@@ -192,6 +192,8 @@ public abstract class CompilerTestCase extends TestCase {
   /** A minimal set of externs, consisting of only those needed for NTI not to blow up. */
   protected static final String MINIMAL_EXTERNS =
       LINE_JOINER.join(
+          "/** @type {undefined} */",
+          "var undefined;",
           "/**",
           " * @constructor",
           " * @param {*=} opt_value",
diff --git a/test/com/google/javascript/jscomp/OptimizeParametersTest.java b/test/com/google/javascript/jscomp/OptimizeParametersTest.java
index 1eb183902f2..70e1f5c2138 100644
--- a/test/com/google/javascript/jscomp/OptimizeParametersTest.java
+++ b/test/com/google/javascript/jscomp/OptimizeParametersTest.java
@@ -24,7 +24,7 @@
 public final class OptimizeParametersTest extends CompilerTestCase {
 
   public OptimizeParametersTest() {
-    super(lines(DEFAULT_EXTERNS, "var undefined;"));
+    super(DEFAULT_EXTERNS);
   }
 
   @Override