diff --git a/table/table.go b/table/table.go
index 73b48c041..0dfc9d2f0 100644
--- a/table/table.go
+++ b/table/table.go
@@ -432,7 +432,7 @@ func (t *Table) block(idx int) (*block, error) {
 
 func (t *Table) blockCacheKey(idx int) uint64 {
 	y.AssertTrue(t.ID() < math.MaxUint32)
-	y.AssertTrue(idx < math.MaxUint32)
+	y.AssertTrue(uint32(idx) < math.MaxUint32)
 	return (t.ID() << 32) | uint64(idx)
 }