diff --git a/tests/suites/test_suite_pkwrite.function b/tests/suites/test_suite_pkwrite.function
index cbe1c1c1e..1c98bd143 100644
--- a/tests/suites/test_suite_pkwrite.function
+++ b/tests/suites/test_suite_pkwrite.function
@@ -25,16 +25,16 @@ void pk_write_pubkey_check( char *key_file )
     mbedtls_pk_init( &key );
     TEST_ASSERT( mbedtls_pk_parse_public_keyfile( &key, key_file ) == 0 );
 
-    ret = mbedtls_pk_write_pubkey_pem( &key, buf, sizeof( buf ) - 1);
-    TEST_ASSERT( ret >= 0 );
+    ret = mbedtls_pk_write_pubkey_pem( &key, buf, sizeof( buf ));
+    TEST_ASSERT( ret == 0 );
 
     f = fopen( key_file, "r" );
     TEST_ASSERT( f != NULL );
-    ilen = fread( check_buf, 1, sizeof( check_buf ) - 1, f );
+    ilen = fread( check_buf, 1, sizeof( check_buf ), f );
     fclose( f );
 
     TEST_ASSERT( ilen == strlen( (char *) buf ) );
-    TEST_ASSERT( strncmp( (char *) buf, (char *) check_buf, sizeof( buf ) ) == 0 );
+    TEST_ASSERT( memcmp( (char *) buf, (char *) check_buf, ilen ) == 0 );
 
 exit:
     mbedtls_pk_free( &key );
@@ -57,16 +57,16 @@ void pk_write_key_check( char *key_file )
     mbedtls_pk_init( &key );
     TEST_ASSERT( mbedtls_pk_parse_keyfile( &key, key_file, NULL ) == 0 );
 
-    ret = mbedtls_pk_write_key_pem( &key, buf, sizeof( buf ) - 1);
+    ret = mbedtls_pk_write_key_pem( &key, buf, sizeof( buf ));
     TEST_ASSERT( ret >= 0 );
 
     f = fopen( key_file, "r" );
     TEST_ASSERT( f != NULL );
-    ilen = fread( check_buf, 1, sizeof( check_buf ) - 1, f );
+    ilen = fread( check_buf, 1, sizeof( check_buf ), f );
     fclose( f );
 
     TEST_ASSERT( ilen == strlen( (char *) buf ) );
-    TEST_ASSERT( strncmp( (char *) buf, (char *) check_buf, sizeof( buf ) ) == 0 );
+    TEST_ASSERT( memcmp( (char *) buf, (char *) check_buf, ilen ) == 0 );
 
 exit:
     mbedtls_pk_free( &key );