diff --git a/examples/nvram/seal_nv.c b/examples/nvram/seal_nv.c
index 85b22748..ed67589a 100644
--- a/examples/nvram/seal_nv.c
+++ b/examples/nvram/seal_nv.c
@@ -196,7 +196,14 @@ int TPM2_NVRAM_SealNV_Example(void* userCtx, int argc, char *argv[])
     /* Set owner auth */
     parent.hndl = TPM_RH_OWNER;
     if (XSTRLEN(ownerAuth) > 0) {
-        parent.auth.size = (int)XSTRLEN(ownerAuth);
+        size_t authLen = XSTRLEN(ownerAuth);
+        if (authLen > sizeof(parent.auth.buffer)) {
+            fprintf(stderr, "-ownerauth value too long (max %zu)\n",
+                sizeof(parent.auth.buffer));
+            rc = BUFFER_E;
+            goto exit;
+        }
+        parent.auth.size = (UINT16)authLen;
         XMEMCPY(parent.auth.buffer, ownerAuth, parent.auth.size);
     }