diff --git a/library/bignum.c b/library/bignum.c
index d59a5d791c..9bc1c2d43f 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1254,10 +1254,10 @@ static mbedtls_mpi_uint mbedtls_int_div_int(mbedtls_mpi_uint u1,
      */
     if (0 == d || u1 >= d) {
         if (r != NULL) {
-            *r = ~0;
+            *r = ~(mbedtls_mpi_uint) 0u;
         }
 
-        return ~0;
+        return ~(mbedtls_mpi_uint) 0u;
     }
 
 #if defined(MBEDTLS_HAVE_UDBL)
@@ -1403,7 +1403,7 @@ int mbedtls_mpi_div_mpi(mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A,
 
     for (i = n; i > t; i--) {
         if (X.p[i] >= Y.p[t]) {
-            Z.p[i - t - 1] = ~0;
+            Z.p[i - t - 1] = ~(mbedtls_mpi_uint) 0u;
         } else {
             Z.p[i - t - 1] = mbedtls_int_div_int(X.p[i], X.p[i - 1],
                                                  Y.p[t], NULL);