diff --git a/os/mitauth.c b/os/mitauth.c
index 867e0cb02..ac519b807 100644
--- a/os/mitauth.c
+++ b/os/mitauth.c
@@ -49,7 +49,16 @@ static struct auth {
 XID
 MitAddCookie(unsigned short data_length, const char *data)
 {
-    struct auth *new = calloc(1, sizeof(struct auth));
+    struct auth *new;
+
+    // check for possible duplicate and return it instead
+    for (struct auth *walk=mit_auth; walk; walk=walk->next) {
+        if ((walk->len == data_length) &&
+            (memcmp(walk->data, data, data_length) == 0))
+            return walk->id;
+    }
+
+    new = calloc(1, sizeof(struct auth));
     if (!new)
         return 0;
     new->data = calloc(1, (unsigned) data_length);
diff --git a/os/xdmauth.c b/os/xdmauth.c
index f96740673..2047b7173 100644
--- a/os/xdmauth.c
+++ b/os/xdmauth.c
@@ -353,6 +353,14 @@ XdmAddCookie(unsigned short data_length, const char *data)
     /* the first octet of the key must be zero */
     if (key_bits[0] != '\0')
         return 0;
+
+    /* check for possible duplicate and return it */
+    for (XdmAuthorizationRec *walk = xdmAuth; walk; walk=walk->next) {
+        if ((memcmp(walk->key.data, key_bits, 8)==0) &&
+            (memcmp(walk->rho.data, rho_bits, 8)==0))
+            return walk->id;
+    }
+
     XdmAuthorizationPtr new = calloc(1, sizeof(XdmAuthorizationRec));
     if (!new)
         return 0;