--- a/dom/canvas/WebGL2ContextState.cpp
+++ b/dom/canvas/WebGL2ContextState.cpp
@@ -113,17 +113,17 @@ WebGL2Context::GetParameter(JSContext* c
     /* GLint64 */
     case LOCAL_GL_MAX_CLIENT_WAIT_TIMEOUT_WEBGL:
       return JS::NumberValue(0); // TODO
 
     case LOCAL_GL_MAX_ELEMENT_INDEX:
       // GL_MAX_ELEMENT_INDEX becomes available in GL 4.3 or via ES3
       // compatibility
       if (!gl->IsSupported(gl::GLFeature::ES3_compatibility))
-        return JS::NumberValue(0);
+        return JS::NumberValue(UINT32_MAX);
 
       /*** fall through to fGetInteger64v ***/
       MOZ_FALLTHROUGH;
 
     case LOCAL_GL_MAX_COMBINED_FRAGMENT_UNIFORM_COMPONENTS:
     case LOCAL_GL_MAX_COMBINED_VERTEX_UNIFORM_COMPONENTS:
     case LOCAL_GL_MAX_UNIFORM_BLOCK_SIZE: {
       GLint64 val;