diff --git a/third_party/github.com/camlistore/goexif/tiff/tag.go b/third_party/github.com/camlistore/goexif/tiff/tag.go
index 2ad3b1de3..d41c2dae0 100644
--- a/third_party/github.com/camlistore/goexif/tiff/tag.go
+++ b/third_party/github.com/camlistore/goexif/tiff/tag.go
@@ -114,7 +114,9 @@ func (t *Tag) convertVals() {
 
 	switch t.Fmt {
 	case 2: // ascii string
-		t.strVal = string(t.Val[:len(t.Val)-1])
+		if len(t.Val) > 0 {
+			t.strVal = string(t.Val[:len(t.Val)-1])
+		}
 	case 1:
 		var v uint8
 		t.intVals = make([]int64, int(t.Ncomp))