diff --git a/src/tag/Mask.hxx b/src/tag/Mask.hxx
index ee269b6e0..fc7ab77da 100644
--- a/src/tag/Mask.hxx
+++ b/src/tag/Mask.hxx
@@ -26,6 +26,11 @@
 
 class TagMask {
 	typedef uint_least32_t mask_t;
+
+	/* the mask must have enough bits to represent all tags
+	   supported by MPD */
+	static_assert(TAG_NUM_OF_ITEM_TYPES <= sizeof(mask_t) * 8);
+
 	mask_t value;
 
 	explicit constexpr TagMask(uint_least32_t _value) noexcept