diff --git a/library/bignum_core.c b/library/bignum_core.c
index 13fc074a6d..bb6e7cd3bc 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -300,19 +300,8 @@ mbedtls_mpi_uint mbedtls_mpi_core_add_if( mbedtls_mpi_uint *A,
 {
     mbedtls_mpi_uint c = 0;
 
-    /* MSVC has a warning about unary minus on unsigned integer types,
-     * but this is well-defined and precisely what we want to do here. */
-#if defined(_MSC_VER)
-#pragma warning( push )
-#pragma warning( disable : 4146 )
-#endif
-
-    /* all-bits 1 if cond is 1, all-bits 0 if cond is 0 */
-    const mbedtls_mpi_uint mask = -(mbedtls_mpi_uint)cond;
-
-#if defined(_MSC_VER)
-#pragma warning( pop )
-#endif
+    /* all-bits 0 if cond is 0, all-bits 1 if cond is non-0 */
+    const mbedtls_mpi_uint mask = mbedtls_ct_mpi_uint_mask( cond );
 
     for( size_t i = 0; i < limbs; i++ )
     {