diff --git a/src/tag/Mask.hxx b/src/tag/Mask.hxx
index 625427174..5a03a5d95 100644
--- a/src/tag/Mask.hxx
+++ b/src/tag/Mask.hxx
@@ -62,7 +62,7 @@ public:
 	}
 
 	TagMask &operator&=(TagMask other) {
-		value |= other.value;
+		value &= other.value;
 		return *this;
 	}