diff --git a/config.def.h b/config.def.h
index 29a1f0d..40ef4e9 100644
--- a/config.def.h
+++ b/config.def.h
@@ -206,6 +206,7 @@ ResourcePref resources[] = {
 		{ "borderpx",     INTEGER, &borderpx },
 		{ "cwscale",      FLOAT,   &cwscale },
 		{ "chscale",      FLOAT,   &chscale },
+		{ "alpha",        FLOAT,   &alpha },
 };
 
 /*