diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 0ebfcca6e55..83144d9124f 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -918,13 +918,18 @@ 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)
 	{
 		appendPQExpBuffer(&conn->errorMessage,
-						  libpq_gettext("drained only %zu of %zd pending bytes in transport buffer\n"),
+						  libpq_gettext("drained only %zd of %zd pending bytes in transport buffer\n"),
 						  nread, bytes_pending);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index acf01433ffc..f7e1c9beeac 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -288,8 +288,9 @@ 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)