diff --git a/src/lib/CoAlgFormula.ml b/src/lib/CoAlgFormula.ml
index 422a926cc9a5ce6958553ed25225c1f1715b6a68..bd52c9dc7bda66cd4a7d37e6c6e474fe04db7095 100644
--- a/src/lib/CoAlgFormula.ml
+++ b/src/lib/CoAlgFormula.ml
@@ -153,7 +153,7 @@ let rec convert_post func formula = (* run over all subformulas in post order *)
   (* replace parts of the formula *)
   let formula = (match formula with
   (* 0-ary constructors *)
-  | TRUE | FALSE | AP _ -> formula
+  | TRUE | FALSE | AP _ | VAR _ -> formula
   | CONST _
   | CONSTN _ -> formula
   (* unary *)
@@ -178,7 +178,15 @@ let rec convert_post func formula = (* run over all subformulas in post order *)
   | NORM(a, b) -> NORM(c a, c b)
   | NORMN(a, b) -> NORMN(c a, c b)
   | CHC (a,b) -> CHC (c a, c b)
-  | FUS (s,a) -> FUS (s, c a)) in
+  | FUS (s,a) -> FUS (s, c a)
+  | MU (n, f1) -> MU (n, c f1)
+  | NU (n, f1) -> NU (n, c f1)
+  | AF f1 -> AF (c f1)
+  | EF f1 -> EF (c f1)
+  | AG f1 -> AG (c f1)
+  | EG f1 -> EG (c f1)
+  | AU (f1, f2) -> AU (c f1, c f2)
+  | EU (f1, f2) -> AU (c f1, c f2))in
   func formula
 
 let convertToK formula = (* tries to convert a formula to a pure K formula *)