diff --git a/src/http_ana.c b/src/http_ana.c
index 188cb7307..078d8beb6 100644
--- a/src/http_ana.c
+++ b/src/http_ana.c
@@ -5213,8 +5213,10 @@ struct http_txn *http_create_txn(struct stream *s)
 
 	txn->auth.method = HTTP_AUTH_UNKNOWN;
 
-	vars_init_head(&s->vars_txn,    SCOPE_TXN);
-	vars_init_head(&s->vars_reqres, SCOPE_REQ);
+	/* here we don't want to re-initialize s->vars_txn and s->vars_reqres
+	 * variable lists, because they were already initialized upon stream
+	 * creation in stream_new(), and thus may already contain some variables
+	 */
 
 	return txn;
 }
diff --git a/src/stream.c b/src/stream.c
index 59d84b921..9906b2141 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -437,8 +437,17 @@ struct stream *stream_new(struct session *sess, struct stconn *sc, struct buffer
 	s->req_cap = NULL;
 	s->res_cap = NULL;
 
-	/* Initialise all the variables contexts even if not used.
+	/* Initialize all the variables contexts even if not used.
 	 * This permits to prune these contexts without errors.
+	 *
+	 * We need to make sure that those lists are not re-initialized
+	 * by stream-dependant underlying code because we could lose
+	 * track of already defined variables, leading to data inconsistency
+	 * and memory leaks...
+	 *
+	 * For reference: we had a very old bug caused by vars_txn and
+	 * vars_reqres being accidentally re-initialized in http_create_txn()
+	 * (https://github.com/haproxy/haproxy/issues/1935)
 	 */
 	vars_init_head(&s->vars_txn,    SCOPE_TXN);
 	vars_init_head(&s->vars_reqres, SCOPE_REQ);