diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 7e02fcc2452..c5e1d13d6f7 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -914,13 +914,18 @@ pqDrainPending(PGconn *conn)
 
 	nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
 						  bytes_pending);
-	conn->inEnd += nread;
 
-	/* When there are bytes pending, the read function is not supposed to fail */
+	/*
+	 * When there are bytes pending, pqsecure_read() is not supposed to fail
+	 * or do a short read, but let's check anyway to be safe.
+	 */
+	if (nread < 0)
+		return -1;
+	conn->inEnd += nread;
 	if (nread != bytes_pending)
 	{
 		libpq_append_conn_error(conn,
-								"drained only %zu of %zd pending bytes in transport buffer",
+								"drained only %zd of %zd pending bytes in transport buffer",
 								nread, bytes_pending);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 42e8dc0d331..6c48edb983a 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -284,8 +284,9 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
  *	Return the number of bytes available in the transport buffer.
  *
  * If pqsecure_read() is called for this number of bytes, it's guaranteed to
- * return successfully without reading from the underlying socket.  See
- * pqDrainPending() for a more complete discussion of the concepts involved.
+ * return successfully with the same number of bytes, without reading from the
+ * underlying socket.  See pqDrainPending() for a more complete discussion of
+ * the concepts involved.
  */
 ssize_t
 pqsecure_bytes_pending(PGconn *conn)