diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 72ba687d3..de92897f5 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -3232,7 +3232,7 @@ mbedtls_ssl_srtp_profile mbedtls_ssl_get_dtls_srtp_protection_profile( const mbe
  *
  * \return         0 on succes, MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL if the key buffer is too small to hold the generated key
  */
-int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, const size_t key_buffer_len, size_t *key_len );
+int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, size_t *key_len );
 #endif /* MBEDTLS_SSL_DTLS_SRTP */
 
 /**
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index ecdd4f636..9f55db439 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4771,11 +4771,11 @@ mbedtls_ssl_srtp_profile mbedtls_ssl_get_dtls_srtp_protection_profile( const mbe
     return( ssl->dtls_srtp_info.chosen_dtls_srtp_profile);
 }
 
-int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, const size_t key_buffer_len, size_t *key_len ) {
+int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, size_t *key_len ) {
     *key_len = 0;
 
     /* check output buffer size */
-    if ( key_buffer_len < ssl->dtls_srtp_info.dtls_srtp_keys_len) {
+    if ( *key_len < ssl->dtls_srtp_info.dtls_srtp_keys_len) {
         return MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
     }