diff --git a/drm_hwcomposer.h b/drm_hwcomposer.h
index 1490438..66c2c81 100644
--- a/drm_hwcomposer.h
+++ b/drm_hwcomposer.h
@@ -171,7 +171,7 @@
     return *this;
   }
 
-  operator bool() {
+  operator bool() const {
     return importer_ != NULL;
   }