diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
index 1a4571c..5ab800c 100644
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -4077,7 +4077,7 @@
         /* The ECDH secret is the premaster secret used for key derivation. */
         unsigned char *psm = ssl->handshake->premaster;
         unsigned char *psm_end = psm + sizeof( ssl->handshake->premaster );
-        size_t zlen;
+        size_t zlen = 0;
 
         /* Compute ECDH shared secret. */
         status = psa_raw_key_agreement( PSA_ALG_ECDH,