diff --git a/stint/intops.nim b/stint/intops.nim
index 9751f05..70a6f83 100644
--- a/stint/intops.nim
+++ b/stint/intops.nim
@@ -94,7 +94,7 @@ func isZero*(x: SomeBigInteger): bool {.inline.} =
   ## false otherwise
   x.data.isZero
 
-func isNegative*(x: SomeBigInteger): bool {.inline.} =
+func isNegative*(x: Stint): bool {.inline.} =
   ## Returns true if input is negative (< 0)
   ## false otherwise
   x.data.isNegative