diff --git a/src/fst/morphology/phonology.twolc b/src/fst/morphology/phonology.twolc
index db93fe6d..b88f26f8 100644
--- a/src/fst/morphology/phonology.twolc
+++ b/src/fst/morphology/phonology.twolc
@@ -233,6 +233,7 @@ Rules
 "ō:o in first syllable"
 !! **Rule: @RULENAME@**
 ō:o <=> # Cns* _  ( i  | u ) Cns:+ (Vow:) [ %^Stress1to2:0 | %^VV2V:0 | %^VowsShU1: ]  ;
+ # Cns* _  ( i  | u ) Cns:+ Vow: Cns: %^Pen:0 %^VV2V:0   ;
 !! rōda+N+Pl+Par
 !!€ rōuda^VV2V^PalatalizeLeft^VowsRM>i
 !!€ rouḑ0000>i