diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 59afb61..d047393 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -470,7 +470,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_mpi_read_string "
-                        "returned -0x%02x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -490,7 +490,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse_file "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -500,7 +500,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_dn_gets "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -524,7 +524,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_csr_parse_file "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -534,7 +534,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509_dn_gets "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -559,7 +559,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_pk_parse_keyfile "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -614,7 +614,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_subject_name "
-                        "returned -0x%02x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -622,7 +622,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_issuer_name "
-                        "returned -0x%02x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -637,7 +637,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_serial "
-                        "returned -0x%02x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -646,7 +646,7 @@
     {
         mbedtls_strerror( ret, buf, 1024 );
         mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_validity "
-                        "returned -0x%02x - %s\n\n", -ret, buf );
+                        "returned -0x%04x - %s\n\n", -ret, buf );
         goto exit;
     }
 
@@ -664,7 +664,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  x509write_crt_set_basic_contraints "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -683,7 +683,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_subject"
-                            "_key_identifier returned -0x%02x - %s\n\n",
+                            "_key_identifier returned -0x%04x - %s\n\n",
                             -ret, buf );
             goto exit;
         }
@@ -702,7 +702,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_authority_"
-                            "key_identifier returned -0x%02x - %s\n\n",
+                            "key_identifier returned -0x%04x - %s\n\n",
                             -ret, buf );
             goto exit;
         }
@@ -722,7 +722,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_key_usage "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -740,7 +740,7 @@
         {
             mbedtls_strerror( ret, buf, 1024 );
             mbedtls_printf( " failed\n  !  mbedtls_x509write_crt_set_ns_cert_type "
-                            "returned -0x%02x - %s\n\n", -ret, buf );
+                            "returned -0x%04x - %s\n\n", -ret, buf );
             goto exit;
         }
 
@@ -757,7 +757,7 @@
                                    mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
         mbedtls_strerror( ret, buf, 1024 );
-        mbedtls_printf( " failed\n  !  write_certificate -0x%02x - %s\n\n",
+        mbedtls_printf( " failed\n  !  write_certificate -0x%04x - %s\n\n",
                         -ret, buf );
         goto exit;
     }