diff --git a/git-gui b/git-gui
index b1a90e6661..7e28328cf0 100755
--- a/git-gui
+++ b/git-gui
@@ -1171,7 +1171,11 @@ proc update_index {pathList} {
 		$totalCnt \
 		0.0]
 	set fd [open "| git update-index --add --remove -z --stdin" w]
-	fconfigure $fd -blocking 0 -translation binary
+	fconfigure $fd \
+		-blocking 0 \
+		-buffering full \
+		-buffersize 512 \
+		-translation binary
 	fileevent $fd writable [list \
 		write_update_index \
 		$fd \