diff --git a/src/idevice.c b/src/idevice.c
index d6c1d06..f64570b 100644
--- a/src/idevice.c
+++ b/src/idevice.c
@@ -650,7 +650,10 @@
 		}
 		debug_info("len %d, sent %d", len, sent);
 		if (sent < len) {
-			*sent_bytes = 0;
+			*sent_bytes = sent;
+			if (sent == 0) {
+				return IDEVICE_E_UNKNOWN_ERROR;
+			}
 			return IDEVICE_E_NOT_ENOUGH_DATA;
 		}
 		*sent_bytes = sent;