diff --git a/doc/portability.dox b/doc/portability.dox
index 1596e55d0..6114973a1 100644
--- a/doc/portability.dox
+++ b/doc/portability.dox
@@ -145,8 +145,8 @@ void main() {
 It is often desirable to query extension presence based on actually used GLSL
 version -- while the extension might be supported in the driver, it might not
 be available in given GLSL version (e.g. causing compilation errors). You can
-use @ref Context::isExtensionSupported(Version) to check that the extension
-is present in given version:
+use @ref Context::isExtensionSupported(Version) const to check that the
+extension is present in given version:
 @code
 if(!Context::instance()->isExtensionSupported<Extensions::GL::ARB::explicit_attrib_location>(version)) {
     bindAttributeLocation(Position::Location, "position");