diff --git a/library/bignum.c b/library/bignum.c
index 6d62e9f..5ec0541 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1605,10 +1605,10 @@
      */
     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)
@@ -1754,7 +1754,7 @@
 
     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);