--- a/dom/canvas/WebGLContextState.cpp
+++ b/dom/canvas/WebGLContextState.cpp
@@ -276,17 +276,16 @@ WebGLContext::GetParameter(JSContext* cx
                 }
                 // TODO: JS doesn't support 64-bit integers. Be lossy and
                 // cast to double (53 bits)
                 return JS::NumberValue(val);
             }
 
         case LOCAL_GL_GPU_DISJOINT_EXT:
             {
-                MOZ_ASSERT(gl->IsExtensionSupported(gl::GLContext::EXT_disjoint_timer_query));
                 realGLboolean val = false;
                 gl->fGetBooleanv(pname, &val);
                 return JS::BooleanValue(val);
             }
 
         default:
             break;
         }