diff --git a/test/completion.js b/test/completion.js
index 47aa8d02..46677ffa 100644
--- a/test/completion.js
+++ b/test/completion.js
@@ -38,4 +38,15 @@ describe('flag: --completion', function() {
     }
   });
 
+  it('shows error message for missing completion type', function(done) {
+    runner({ verbose: false })
+      .gulp('--completion')
+      .run(cb);
+
+    function cb(err, stdout, stderr) {
+      expect(stderr).toMatch('Missing completion type');
+      done();
+    }
+  });
+
 });
diff --git a/test/fixtures/gulpfiles/gulpfile-exports.babel.js b/test/fixtures/gulpfiles/gulpfile-exports.babel.js
index 514fdb30..1ebf6b62 100644
--- a/test/fixtures/gulpfiles/gulpfile-exports.babel.js
+++ b/test/fixtures/gulpfiles/gulpfile-exports.babel.js
@@ -6,4 +6,5 @@ import gulp from 'gulp';
 
 export function clean(){};
 export function build(){};
+export const string = 'no function';
 export const dist = gulp.series(clean, build);