diff --git a/tests/SkRuntimeEffectTest.cpp b/tests/SkRuntimeEffectTest.cpp
index e7aeb3f..b3a5522 100644
--- a/tests/SkRuntimeEffectTest.cpp
+++ b/tests/SkRuntimeEffectTest.cpp
@@ -56,6 +56,9 @@
     test("layout(marker=local_to_world) uniform float3x3 localToWorld;", "", "float4x4");
 
     test("half missing();", "color.r = missing();", "undefined function");
+
+    // Shouldn't be possible to create an SkRuntimeEffect without "main"
+    test("//", "", "main");
 }
 
 class TestEffect {