diff --git a/programs/ssl/dtls_client.c b/programs/ssl/dtls_client.c
index 3ea2a68..ce1056f 100644
--- a/programs/ssl/dtls_client.c
+++ b/programs/ssl/dtls_client.c
@@ -149,7 +149,7 @@
                           mbedtls_test_cas_pem_len );
     if( ret < 0 )
     {
-        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -225,7 +225,7 @@
 
     if( ret != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
         goto exit;
     }
 
@@ -303,7 +303,7 @@
                 goto close_notify;
 
             default:
-                mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", -ret );
+                mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", (unsigned int) -ret );
                 goto exit;
         }
     }