diff --git a/src/Magnum/Shaders/MeshVisualizer.cpp b/src/Magnum/Shaders/MeshVisualizer.cpp
index 08d2e6e43..e37997423 100644
--- a/src/Magnum/Shaders/MeshVisualizer.cpp
+++ b/src/Magnum/Shaders/MeshVisualizer.cpp
@@ -60,10 +60,10 @@ MeshVisualizer::MeshVisualizer(const Flags flags): flags(flags), transformationP
 
     #ifndef MAGNUM_TARGET_GLES
     const Version version = Context::current()->supportedVersion({Version::GL320, Version::GL310, Version::GL300, Version::GL210});
-    CORRADE_INTERNAL_ASSERT(flags & Flag::NoGeometryShader || version >= Version::GL320);
+    CORRADE_INTERNAL_ASSERT(!flags || flags & Flag::NoGeometryShader || version >= Version::GL320);
     #else
     const Version version = Context::current()->supportedVersion({Version::GLES310, Version::GLES300, Version::GLES200});
-    CORRADE_INTERNAL_ASSERT(flags & Flag::NoGeometryShader || version >= Version::GLES310);
+    CORRADE_INTERNAL_ASSERT(!flags || flags & Flag::NoGeometryShader || version >= Version::GLES310);
     #endif
 
     Shader vert = Implementation::createCompatibilityShader(rs, version, Shader::Type::Vertex);