diff --git a/src/openvpn/dco_win.c b/src/openvpn/dco_win.c
index 4dd307f..30307de 100644
--- a/src/openvpn/dco_win.c
+++ b/src/openvpn/dco_win.c
@@ -541,7 +541,7 @@
     ZeroMemory(&crypto_data, sizeof(crypto_data));
 
     crypto_data.CipherAlg = dco_get_cipher(ciphername);
-    ASSERT(keyid > 0 && keyid <= UCHAR_MAX);
+    ASSERT(keyid >= 0 && keyid <= UCHAR_MAX);
     crypto_data.KeyId = (unsigned char)keyid;
     crypto_data.PeerId = peerid;
     crypto_data.KeySlot = slot;