diff --git a/src/util/bitset.h b/src/util/bitset.h
index 3c90a2aaf19..bc324bc435f 100644
--- a/src/util/bitset.h
+++ b/src/util/bitset.h
@@ -282,6 +282,7 @@ __bitset_clear_range(BITSET_WORD *r, int start, int end)
 static inline unsigned
 __bitset_extract(const BITSET_WORD *r, unsigned start, unsigned count)
 {
+   assert(count <= BITSET_WORDBITS);
    unsigned shift = start % BITSET_WORDBITS;
    BITSET_WORD lower = r[BITSET_BITWORD(start)] >> shift;
    BITSET_WORD upper = shift ? r[BITSET_BITWORD(start + count - 1)] << (BITSET_WORDBITS - shift) : 0;