diff --git a/tests/suites/test_suite_pkwrite.function b/tests/suites/test_suite_pkwrite.function
index 491bc489aa..a07c5dec2a 100644
--- a/tests/suites/test_suite_pkwrite.function
+++ b/tests/suites/test_suite_pkwrite.function
@@ -66,15 +66,46 @@ static int pk_write_any_key(mbedtls_pk_context *pk, unsigned char **p,
     return 0;
 }
 
+static void pk_write_check_context(mbedtls_pk_context *key,
+                                   int is_public_key, int is_der,
+                                   unsigned char *check_buf, size_t check_buf_len)
+{
+    unsigned char *buf = NULL;
+    size_t buf_len;
+    unsigned char *start_buf;
+    int expected_result;
+
+    TEST_CALLOC(buf, check_buf_len);
+
+    start_buf = buf;
+    buf_len = check_buf_len;
+    if (is_der) {
+        expected_result = MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    } else {
+        expected_result = MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
+    }
+    /* Intentionally pass a wrong size for the provided output buffer and check
+     * that the writing functions fails as expected. */
+    for (size_t i = 1; i < buf_len; i++) {
+        TEST_EQUAL(pk_write_any_key(key, &start_buf, &i, is_public_key,
+                                    is_der), expected_result);
+    }
+    TEST_EQUAL(pk_write_any_key(key, &start_buf, &buf_len, is_public_key,
+                                is_der), 0);
+
+    TEST_MEMORY_COMPARE(start_buf, buf_len, check_buf, check_buf_len);
+
+exit:
+    mbedtls_free(buf);
+}
+
+
 static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
 {
     mbedtls_pk_context key;
     mbedtls_pk_init(&key);
-    unsigned char *buf = NULL;
     unsigned char *check_buf = NULL;
-    unsigned char *start_buf;
-    size_t buf_len, check_buf_len;
-    int expected_result;
+    size_t check_buf_len;
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     mbedtls_svc_key_id_t opaque_id = MBEDTLS_SVC_KEY_ID_INIT;
     psa_key_attributes_t key_attr = PSA_KEY_ATTRIBUTES_INIT;
@@ -100,8 +131,6 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
     }
     TEST_ASSERT(check_buf_len > 0);
 
-    TEST_CALLOC(buf, check_buf_len);
-
     if (is_public_key) {
         TEST_EQUAL(mbedtls_pk_parse_public_keyfile(&key, key_file), 0);
     } else {
@@ -109,28 +138,12 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
                                             mbedtls_test_rnd_std_rand, NULL), 0);
     }
 
-    start_buf = buf;
-    buf_len = check_buf_len;
-    if (is_der) {
-        expected_result = MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
-    } else {
-        expected_result = MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
-    }
-    /* Intentionally pass a wrong size for the provided output buffer and check
-     * that the writing functions fails as expected. */
-    for (size_t i = 1; i < buf_len; i++) {
-        TEST_EQUAL(pk_write_any_key(&key, &start_buf, &i, is_public_key,
-                                    is_der), expected_result);
-    }
-    TEST_EQUAL(pk_write_any_key(&key, &start_buf, &buf_len, is_public_key,
-                                is_der), 0);
-
-    TEST_MEMORY_COMPARE(start_buf, buf_len, check_buf, check_buf_len);
+    pk_write_check_context(&key, is_public_key, is_der,
+                           check_buf, check_buf_len);
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     /* Verify that pk_write works also for opaque private keys */
     if (!is_public_key) {
-        memset(buf, 0, check_buf_len);
         /* Turn the key PK context into an opaque one.
          * Note: set some practical usage for the key to make get_psa_attributes() happy. */
         TEST_EQUAL(mbedtls_pk_get_psa_attributes(&key, PSA_KEY_USAGE_SIGN_MESSAGE, &key_attr), 0);
@@ -138,18 +151,9 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
         mbedtls_pk_free(&key);
         mbedtls_pk_init(&key);
         TEST_EQUAL(mbedtls_pk_setup_opaque(&key, opaque_id), 0);
-        start_buf = buf;
-        buf_len = check_buf_len;
-        /* Intentionally pass a wrong size for the provided output buffer and check
-         * that the writing functions fails as expected. */
-        for (size_t i = 1; i < buf_len; i++) {
-            TEST_EQUAL(pk_write_any_key(&key, &start_buf, &i, is_public_key,
-                                        is_der), expected_result);
-        }
-        TEST_EQUAL(pk_write_any_key(&key, &start_buf, &buf_len, is_public_key,
-                                    is_der), 0);
 
-        TEST_MEMORY_COMPARE(start_buf, buf_len, check_buf, check_buf_len);
+        pk_write_check_context(&key, is_public_key, is_der,
+                               check_buf, check_buf_len);
     }
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 
@@ -157,7 +161,6 @@ exit:
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     psa_destroy_key(opaque_id);
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
-    mbedtls_free(buf);
     mbedtls_free(check_buf);
     mbedtls_pk_free(&key);
     USE_PSA_DONE();