diff --git a/src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp b/src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp
index ca8b908a5..d4e6a183a 100644
--- a/src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp
+++ b/src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp
@@ -2650,7 +2650,8 @@ template<MeshVisualizerGL2D::Flag flag> void MeshVisualizerGLTest::renderWirefra
 
     GL::Mesh circle{NoCreate};
     if(data.flags & MeshVisualizerGL2D::Flag::NoGeometryShader) {
-        /* Duplicate the vertices. The circle primitive is  */
+        /* Duplicate the vertices. The circle primitive is a triangle fan, so
+           we first need to turn it into indexed triangles. */
         const Trade::MeshData circleDataIndexed =
             MeshTools::generateIndices(circleData);
         circle = MeshTools::compile(MeshTools::duplicate(circleDataIndexed));