diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index e0d88b207..bffc4ab86 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -816,7 +816,7 @@ int main( int argc, char *argv[] )
         if( ret != 0 )
         {
             mbedtls_strerror( ret, buf, 1024 );
-            mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_ext_key_usage returned -0x%02x - %s\n\n", -ret, buf );
+            mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_ext_key_usage returned -0x%02x - %s\n\n", (unsigned int) -ret, buf );
             goto exit;
         }
 
diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index 324223252..5781fe0d8 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -349,7 +349,8 @@ void x509_crt_check( char *subject_key_file, char *subject_pwd,
             TEST_ASSERT( mbedtls_x509write_crt_set_ns_cert_type( &crt, cert_type ) == 0 );
         if( strcmp( ext_key_usage, "NULL" ) != 0 )
         {
-            mbedtls_asn1_sequence exts[2] = { };
+            mbedtls_asn1_sequence exts[2];
+            memset(exts, 0, sizeof(exts));
 #define SET_OID(x, oid) \
     do { x.len = MBEDTLS_OID_SIZE(oid); x.p = (unsigned char*)oid; \
          x.tag = MBEDTLS_ASN1_OID; } while( 0 )