diff --git a/NEWS b/NEWS
index 0b71653f..86751c4f 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,7 @@ Current release
 What's new in psycopg 2.6.1
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Correctly unlock the connection after error in flush (:ticket:`#294`).
 - Fixed ``MinTimeLoggingCursor.callproc()`` (:ticket:`#309`).
 
 
diff --git a/psycopg/pqpath.c b/psycopg/pqpath.c
index c4b5528d..5e1974be 100644
--- a/psycopg/pqpath.c
+++ b/psycopg/pqpath.c
@@ -980,6 +980,10 @@ pq_execute(cursorObject *curs, const char *query, int async, int no_result, int
         }
         else {
             /* there was an error */
+            pthread_mutex_unlock(&(curs->conn->lock));
+            Py_BLOCK_THREADS;
+            PyErr_SetString(OperationalError,
+                            PQerrorMessage(curs->conn->pgconn));
             return -1;
         }
     }