diff --git a/library/bignum.c b/library/bignum.c
index 225e36c..e00204b 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1666,7 +1666,7 @@
      * calculating the result is trivial in those cases. */
     if( b == 0 || n == 0 )
     {
-        return mbedtls_mpi_lset( X, 0 );
+        return( mbedtls_mpi_lset( X, 0 ) );
     }
 
     /* Calculate A*b as A + A*(b-1) to take advantage of mpi_mul_hlp */