diff --git a/lib/tls/mbedtls/wrapper/library/ssl_lib.c b/lib/tls/mbedtls/wrapper/library/ssl_lib.c
index 25408aa0e..a3220d69a 100644
--- a/lib/tls/mbedtls/wrapper/library/ssl_lib.c
+++ b/lib/tls/mbedtls/wrapper/library/ssl_lib.c
@@ -238,8 +238,10 @@ void SSL_CTX_free(SSL_CTX* ctx)
 
     X509_free(ctx->client_CA);
 
-    if (ctx->alpn_protos)
+    if (ctx->alpn_protos) {
 	    ssl_mem_free((void *)ctx->alpn_protos);
+	    ctx->alpn_protos = NULL;
+    }
 
     ssl_mem_free(ctx);
 }
@@ -353,8 +355,10 @@ void SSL_free(SSL *ssl)
 
     SSL_SESSION_free(ssl->session);
 
-    if (ssl->alpn_protos)
+    if (ssl->alpn_protos) {
 	    ssl_mem_free((void *)ssl->alpn_protos);
+	    ssl->alpn_protos = NULL;
+    }
 
     ssl_mem_free(ssl);
 }