diff --git a/library/bignum.c b/library/bignum.c
index 8a061df..2a7786f 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1728,7 +1728,7 @@
 
     for (size_t i = 0; i < T_size; i++) {
         MBEDTLS_MPI_CHK(mbedtls_mpi_safe_cond_assign(R, &T[i],
-                                                     (unsigned char) mbedtls_ct_bool_eq(i, idx)));
+                                                     (unsigned char) mbedtls_ct_uint_eq(i, idx)));
     }
 cleanup:
     return ret;