diff --git a/lib/asyn-thread.c b/lib/asyn-thread.c
index b8c304943d..8d6a9deb4a 100644
--- a/lib/asyn-thread.c
+++ b/lib/asyn-thread.c
@@ -138,14 +138,14 @@ CURLcode Curl_resolver_duphandle(struct Curl_easy *easy, void **to, void *from)
   return Curl_resolver_init(easy, to);
 }
 
-static void destroy_async_data(struct Curl_async *);
+static void destroy_async_data(struct Curl_easy *);
 
 /*
  * Cancel all possibly still on-going resolves for this connection.
  */
 void Curl_resolver_cancel(struct Curl_easy *data)
 {
-  destroy_async_data(&data->state.async);
+  destroy_async_data(data);
 }
 
 /* This function is used to init a threaded resolve */
@@ -377,14 +377,17 @@ CURL_STDCALL gethostbyname_thread(void *arg)
 /*
  * destroy_async_data() cleans up async resolver data and thread handle.
  */
-static void destroy_async_data(struct Curl_async *async)
+static void destroy_async_data(struct Curl_easy *data)
 {
+  struct Curl_async *async;
+  DEBUGASSERT(data);
+  async = &data->state.async;
+  DEBUGASSERT(async);
   if(async->tdata) {
     struct thread_data *td = async->tdata;
     bool done;
 #ifndef CURL_DISABLE_SOCKETPAIR
     curl_socket_t sock_rd = td->tsd.sock_pair[0];
-    struct Curl_easy *data = td->tsd.data;
 #endif
 
 #ifdef USE_HTTPSRR_ARES
@@ -500,7 +503,7 @@ static bool init_resolve_thread(struct Curl_easy *data,
   return TRUE;
 
 err_exit:
-  destroy_async_data(asp);
+  destroy_async_data(data);
 
 errno_exit:
   errno = err;
@@ -539,7 +542,7 @@ static CURLcode thread_wait_resolv(struct Curl_easy *data,
     /* a name was not resolved, report error */
     result = Curl_resolver_error(data);
 
-  destroy_async_data(&data->state.async);
+  destroy_async_data(data);
 
   if(!data->state.async.dns && report)
     connclose(data->conn, "asynch resolve failed");
@@ -617,7 +620,7 @@ CURLcode Curl_resolver_is_resolved(struct Curl_easy *data,
 
     if(!data->state.async.dns) {
       CURLcode result = Curl_resolver_error(data);
-      destroy_async_data(&data->state.async);
+      destroy_async_data(data);
       return result;
     }
 #ifdef USE_HTTPSRR_ARES
@@ -625,13 +628,13 @@ CURLcode Curl_resolver_is_resolved(struct Curl_easy *data,
       struct Curl_https_rrinfo *lhrr =
         Curl_memdup(&td->hinfo, sizeof(struct Curl_https_rrinfo));
       if(!lhrr) {
-        destroy_async_data(&data->state.async);
+        destroy_async_data(data);
         return CURLE_OUT_OF_MEMORY;
       }
       data->state.async.dns->hinfo = lhrr;
     }
 #endif
-    destroy_async_data(&data->state.async);
+    destroy_async_data(data);
     *entry = data->state.async.dns;
   }
   else {
@@ -685,7 +688,6 @@ int Curl_resolver_getsock(struct Curl_easy *data, curl_socket_t *socks)
   if(td) {
     /* return read fd to client for polling the DNS resolution status */
     socks[socketi] = td->tsd.sock_pair[0];
-    td->tsd.data = data;
     ret_val = GETSOCK_READSOCK(socketi);
   }
   else {
diff --git a/lib/asyn.h b/lib/asyn.h
index c674541256..5a21329cf3 100644
--- a/lib/asyn.h
+++ b/lib/asyn.h
@@ -40,20 +40,19 @@ struct Curl_dns_entry;
 /* Data for synchronization between resolver thread and its parent */
 struct thread_sync_data {
   curl_mutex_t *mtx;
-  bool done;
-  int port;
   char *hostname;        /* hostname to resolve, Curl_async.hostname
                             duplicate */
 #ifndef CURL_DISABLE_SOCKETPAIR
-  struct Curl_easy *data;
   curl_socket_t sock_pair[2]; /* eventfd/pipes/socket pair */
 #endif
-  int sock_error;
   struct Curl_addrinfo *res;
 #ifdef HAVE_GETADDRINFO
   struct addrinfo hints;
 #endif
   struct thread_data *td; /* for thread-self cleanup */
+  int port;
+  int sock_error;
+  bool done;
 };
 
 struct thread_data {