diff --git a/psycopg/pqpath.c b/psycopg/pqpath.c
index a996bd7..d0a940f 100644
--- a/psycopg/pqpath.c
+++ b/psycopg/pqpath.c
@@ -1322,7 +1322,12 @@ _pq_copy_in_v3(cursorObject *curs)
     }
     else {
         /* and finally we grab the operation result from the backend */
-        while ((curs->pgres = PQgetResult(curs->conn->pgconn)) != NULL) {
+        for (;;) {
+            Py_BEGIN_ALLOW_THREADS;
+            curs->pgres = PQgetResult(curs->conn->pgconn);
+            Py_END_ALLOW_THREADS;
+            if (!curs->pgres)
+                break;
             if (PQresultStatus(curs->pgres) == PGRES_FATAL_ERROR)
                 pq_raise(curs->conn, curs, NULL);
             IFCLEARPGRES(curs->pgres);