diff --git a/phsource/ph_vietnam b/phsource/ph_vietnam
index c6dfb9af..c1dd45d5 100644
--- a/phsource/ph_vietnam
+++ b/phsource/ph_vietnam
@@ -554,6 +554,7 @@ phoneme d_
   vcd alv stp
     //	lengthmod 5
 	ipa ɗ
+	length 50
  Vowelin f1=1  f2=1700 -300 300  f3=-100 80 len=15
   Vowelout f1=2 f2=1700 -300 300  f3=-100 80 brk len=30
 WAV(vietnam/dd)