diff --git a/library/bignum.c b/library/bignum.c
index 86376a4..2d04eb4 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1170,7 +1170,7 @@
 /*
  * Baseline multiplication: X = A * b
  */
-int mpi_mul_int( mpi *X, const mpi *A, t_sint b )
+int mpi_mul_int( mpi *X, const mpi *A, t_uint b )
 {
     mpi _B;
     t_uint p[1];