Index: curl-7.65.3/lib/connect.c
===================================================================
--- curl-7.65.3.orig/lib/connect.c	2021-01-07 17:18:20.075781504 +0800
+++ curl-7.65.3/lib/connect.c	2021-01-07 17:35:29.759365377 +0800
@@ -1239,15 +1239,15 @@
 }
 
 struct connfind {
-  struct connectdata *tofind;
-  bool found;
+  long id_tofind;
+  struct connectdata *found;
 };
 
 static int conn_is_conn(struct connectdata *conn, void *param)
 {
   struct connfind *f = (struct connfind *)param;
-  if(conn == f->tofind) {
-    f->found = TRUE;
+  if(conn->connection_id == f->id_tofind) {
+    f->found = conn;
     return 1;
   }
   return 0;
@@ -1269,21 +1269,22 @@
    * - that is associated with a multi handle, and whose connection
    *   was detached with CURLOPT_CONNECT_ONLY
    */
-  if(data->state.lastconnect && (data->multi_easy || data->multi)) {
-    struct connectdata *c = data->state.lastconnect;
+  if((data->state.lastconnect_id != -1) && (data->multi_easy || data->multi)) {
+    struct connectdata *c;
     struct connfind find;
-    find.tofind = data->state.lastconnect;
-    find.found = FALSE;
+    find.id_tofind = data->state.lastconnect_id;
+    find.found = NULL;
 
     Curl_conncache_foreach(data, data->multi_easy?
                            &data->multi_easy->conn_cache:
                            &data->multi->conn_cache, &find, conn_is_conn);
 
     if(!find.found) {
-      data->state.lastconnect = NULL;
+      data->state.lastconnect_id = -1;
       return CURL_SOCKET_BAD;
     }
 
+    c = find.found;
     if(connp) {
       /* only store this if the caller cares for it */
       *connp = c;
Index: curl-7.65.3/lib/easy.c
===================================================================
--- curl-7.65.3.orig/lib/easy.c	2021-01-07 17:18:20.055781504 +0800
+++ curl-7.65.3/lib/easy.c	2021-01-07 17:35:52.349178075 +0800
@@ -859,7 +859,7 @@
   /* the connection cache is setup on demand */
   outcurl->state.conn_cache = NULL;
 
-  outcurl->state.lastconnect = NULL;
+  outcurl->state.lastconnect_id = -1;
 
   outcurl->progress.flags    = data->progress.flags;
   outcurl->progress.callback = data->progress.callback;
Index: curl-7.65.3/lib/multi.c
===================================================================
--- curl-7.65.3.orig/lib/multi.c	2021-01-07 17:18:20.063781504 +0800
+++ curl-7.65.3/lib/multi.c	2021-01-07 17:36:59.301713317 +0800
@@ -434,6 +434,7 @@
     data->state.conn_cache = &data->share->conn_cache;
   else
     data->state.conn_cache = &multi->conn_cache;
+  data->state.lastconnect_id = -1;
 
 #ifdef USE_LIBPSL
   /* Do the same for PSL. */
@@ -639,11 +640,11 @@
     /* the connection is no longer in use by this transfer */
     if(Curl_conncache_return_conn(conn)) {
       /* remember the most recently used connection */
-      data->state.lastconnect = conn;
+      data->state.lastconnect_id = conn->connection_id;
       infof(data, "%s\n", buffer);
     }
     else
-      data->state.lastconnect = NULL;
+      data->state.lastconnect_id = -1;
   }
 
   Curl_free_request_state(data);
Index: curl-7.65.3/lib/url.c
===================================================================
--- curl-7.65.3.orig/lib/url.c	2021-01-07 17:18:20.091781504 +0800
+++ curl-7.65.3/lib/url.c	2021-01-07 17:39:32.029219004 +0800
@@ -609,7 +609,7 @@
       Curl_initinfo(data);
 
       /* most recent connection is not yet defined */
-      data->state.lastconnect = NULL;
+      data->state.lastconnect_id = -1;
 
       data->progress.flags |= PGRS_HIDE;
       data->state.current_speed = -1; /* init to negative == impossible */
Index: curl-7.65.3/lib/urldata.h
===================================================================
--- curl-7.65.3.orig/lib/urldata.h	2021-01-07 17:18:20.083781504 +0800
+++ curl-7.65.3/lib/urldata.h	2021-01-07 17:40:16.830792026 +0800
@@ -1262,7 +1262,7 @@
   /* buffers to store authentication data in, as parsed from input options */
   struct curltime keeps_speed; /* for the progress meter really */
 
-  struct connectdata *lastconnect; /* The last connection, NULL if undefined */
+  long lastconnect_id; /* The last connection, -1 if undefined */
 
   char *headerbuff; /* allocated buffer to store headers in */
   size_t headersize;   /* size of the allocation */