diff --git a/src/Magnum/Primitives/Plane.cpp b/src/Magnum/Primitives/Plane.cpp
index 479260dd9..99d8a6767 100644
--- a/src/Magnum/Primitives/Plane.cpp
+++ b/src/Magnum/Primitives/Plane.cpp
@@ -37,6 +37,10 @@ constexpr struct VertexSolid {
     Vector3 position;
     Vector3 normal;
 } VerticesSolid[] {
+    /* 3--1
+       | /|
+       |/ |
+       2--0 */
     {{ 1.0f, -1.0f, 0.0f}, {0.0f, 0.0f, 1.0f}},
     {{ 1.0f,  1.0f, 0.0f}, {0.0f, 0.0f, 1.0f}},
     {{-1.0f, -1.0f, 0.0f}, {0.0f, 0.0f, 1.0f}},
diff --git a/src/Magnum/Primitives/Square.cpp b/src/Magnum/Primitives/Square.cpp
index 359ecf7bb..cc25a3df6 100644
--- a/src/Magnum/Primitives/Square.cpp
+++ b/src/Magnum/Primitives/Square.cpp
@@ -38,6 +38,10 @@ namespace {
 constexpr struct VertexSolid {
     Vector2 position;
 } VerticesSolid[] {
+    /* 3--1
+       | /|
+       |/ |
+       2--0 */
     {{ 1.0f, -1.0f}},
     {{ 1.0f,  1.0f}},
     {{-1.0f, -1.0f}},