diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index 37fc47d9d78..eecfeceee15 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -417,7 +417,7 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
         }
         let data = match data {
             Some(data) => data,
-            None => return,
+            None => return self.webgl_error(InvalidValue),
         };
         if offset < 0 {
             return self.webgl_error(InvalidValue);
diff --git a/tests/html/test_webgl_triangle.html b/tests/html/test_webgl_triangle.html
index b55a746b4a2..980049f4466 100644
--- a/tests/html/test_webgl_triangle.html
+++ b/tests/html/test_webgl_triangle.html
@@ -19,9 +19,7 @@
    }
 </script>
 <script id="fragmentshader" type="x-shader">
-   #ifdef GL_ES
-   precision highp float;
-   #endif
+   precision mediump float;
 
    varying vec4 aVertexColor;