diff --git a/NEWS b/NEWS
index 2017932b..704c1b0d 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,7 @@ What's new in psycopg 2.7.2
   (:ticket:`#545`).
 - Fixed `~psycopg2.extras.ReplicationCursor.consume_stream()`
   *keepalive_interval* argument (:ticket:`#547`).
+- Fixed random `!SystemError` upon receiving abort signal (:ticket:`#551`).
 - `~psycopg2.errorcodes` map updated to PostgreSQL 10 beta 1.
 
 
diff --git a/psycopg/pqpath.c b/psycopg/pqpath.c
index 55720724..7e8c8e8b 100644
--- a/psycopg/pqpath.c
+++ b/psycopg/pqpath.c
@@ -1893,8 +1893,12 @@ pq_fetch(cursorObject *curs, int no_result)
     Dprintf("pq_fetch: pgstatus = %s", PQresStatus(pgstatus));
 
     /* backend status message */
-    Py_XDECREF(curs->pgstatus);
-    curs->pgstatus = conn_text_from_chars(curs->conn, PQcmdStatus(curs->pgres));
+    Py_CLEAR(curs->pgstatus);
+    if (!(curs->pgstatus = conn_text_from_chars(
+            curs->conn, PQcmdStatus(curs->pgres)))) {
+        ex = -1;
+        return ex;
+    }
 
     switch(pgstatus) {