diff --git a/src/iostream.c b/src/iostream.c
index 7505495..7d0040d 100644
--- a/src/iostream.c
+++ b/src/iostream.c
@@ -215,6 +215,15 @@ dc_iostream_read (dc_iostream_t *iostream, void *data, size_t size, size_t *actu
 		if (status != DC_STATUS_SUCCESS)
 			return status;
 
+		/*
+		 * Defensive check: if the read() function returned
+		 * zero bytes, don't loop forever - give up with a
+		 * timeout. Jef pointed out that the subsurface
+		 * qt_serial_read() function can cause this badness..
+		 */
+		if (!nbytes)
+			return DC_STATUS_TIMEOUT;
+
 		/*
 		 * Continue reading to fill up the whole buffer,
 		 * since the reader is not able to handle a