diff --git a/tests/src/test_helpers/ssl_helpers.c b/tests/src/test_helpers/ssl_helpers.c
index 16fa38a..21dcdec 100644
--- a/tests/src/test_helpers/ssl_helpers.c
+++ b/tests/src/test_helpers/ssl_helpers.c
@@ -950,7 +950,7 @@
 /*
  * Write application data. Increase write counter if necessary.
  */
-int mbedtls_ssl_write_fragment(mbedtls_ssl_context *ssl,
+static int mbedtls_ssl_write_fragment(mbedtls_ssl_context *ssl,
                                unsigned char *buf, int buf_len,
                                int *written,
                                const int expected_fragments)
@@ -997,7 +997,7 @@
  * Read application data and increase read counter and fragments counter
  * if necessary.
  */
-int mbedtls_ssl_read_fragment(mbedtls_ssl_context *ssl,
+static int mbedtls_ssl_read_fragment(mbedtls_ssl_context *ssl,
                               unsigned char *buf, int buf_len,
                               int *read, int *fragments,
                               const int expected_fragments)