diff --git a/phsource/ph_vietnam b/phsource/ph_vietnam
index 84ada505..05768a8e 100644
--- a/phsource/ph_vietnam
+++ b/phsource/ph_vietnam
@@ -270,11 +270,25 @@ endphoneme
 
 phoneme @:
   vwl  starttype #@  endtype #@
-  IF thisPh(isFirstVowel) AND thisPh(isFinalVowel) AND thisPh(isWordEnd) THEN
+  IF nextPhW(p) THEN
+	length 123
+  ELIF nextPhW(t[) THEN
+	length 123
+  ELIF nextPhW(c) THEN
+	length 139
+  ELIF nextPhW(m) THEN
+	length 127
+  ELIF nextPhW(n) THEN
+	length 160
+  ELIF nextPhW(N) THEN
+	length 156
+  ELIF thisPh(isFirstVowel) AND thisPh(isFinalVowel) AND thisPh(isWordEnd) THEN
 	length 240
-	ELSE
+  ELIF thisPh(isFirstVowel) AND thisPh(isFinalVowel) AND thisPh(isWordStart) THEN
+	length 240
+  ELSE
 	length 180
-	ENDIF
+  ENDIF
   FMT(vowel/@_2)
 endphoneme