diff --git a/haskell/src/Graph.hs b/haskell/src/Graph.hs
index f71dac0..a3f490d 100644
--- a/haskell/src/Graph.hs
+++ b/haskell/src/Graph.hs
@@ -22,6 +22,8 @@ data Graph = Graph
 data UnoOp
   = Neg       -- ^ @= 0@
   | Id        -- ^ @= 1@
+  | Lnot      -- ^ @= 2@
+  | Bnot      -- ^ @= 3@
   deriving (Eq,Enum,Bounded,Show)
 
 data DuoOp 
diff --git a/haskell/src/Semantics.hs b/haskell/src/Semantics.hs
index ddc1f36..5ac6367 100644
--- a/haskell/src/Semantics.hs
+++ b/haskell/src/Semantics.hs
@@ -18,6 +18,8 @@ data PrimOp a
   -- unary
   = Neg  a
   | Id   a
+  | Lnot a
+  | Bnot a
   -- binary
   | Mul  a a
   | Div  a a
@@ -49,6 +51,8 @@ evalPrimOp :: PrimOp F -> F
 evalPrimOp prim = case prim of
   Neg  x     -> neg x
   Id   x     -> x
+  Lnot x     -> fromBool (not (toBool x))
+  Bnot x     -> toF (fieldMask .&. (negate (fromF x) - 1)) 
   Mul  x y   -> mul x y
   Div  x y   -> BN254.div x y
   Add  x y   -> add x y