diff --git a/lib/Bril.hs b/lib/Bril.hs
index 17a9ac0..22e1139 100644
--- a/lib/Bril.hs
+++ b/lib/Bril.hs
@@ -6,7 +6,7 @@ module Bril (
 
 import Data.Aeson (FromJSON, parseJSON, withObject, withText, (.:), (.:?), decode)
 import Data.Aeson.Types (Parser, modifyFailure)
-import qualified Data.Aeson (Value)
+import qualified Data.Aeson (Value, Object, Key)
 import Data.Aeson.KeyMap
 import Data.Int (Int64)
 import qualified Data.Text as T
@@ -115,6 +115,11 @@ instrFromString s
     | s == "nop" = Nop
     | otherwise = error "wrong instruction name"
 
+optionalArrayField :: FromJSON a => Data.Aeson.Object -> Data.Aeson.Key -> Parser [a]
+optionalArrayField v field =
+    ((v .:? field) >>= (return . fromMaybe []))
+
+
 instance FromJSON Program  where
     parseJSON = withObject "Program" $ \v -> Program
         <$> v .: "functions"
@@ -122,8 +127,8 @@ instance FromJSON Program  where
 instance FromJSON Function where
     parseJSON = withObject "Function" $ \v -> Function
         <$> v .: "name"
-        <*> v .: "type"
-        <*> v .: "args"
+        <*> v .:? "type"
+        <*> v `optionalArrayField` "args"
         <*> v .: "instrs"
 
 instance FromJSON Instruction where
@@ -146,9 +151,9 @@ instance FromJSON Instruction where
                 <*> v .: "dest"
         parseValueInstr op v = do
             dest  <- (v .: "dest") :: Parser VarName
-            args  <- ((v .:? "args") >>= (return . fromMaybe [])) :: Parser [VarName]
-            labels  <- ((v .:? "labels") >>= (return . fromMaybe [])) :: Parser [VarName]
-            funcs  <- ((v .:? "funcs") >>= (return . fromMaybe [])) :: Parser [VarName]
+            args  <- (v `optionalArrayField` "args") :: Parser [VarName]
+            labels  <- (v `optionalArrayField` "labels") :: Parser [VarName]
+            funcs  <- (v `optionalArrayField` "funcs") :: Parser [VarName]
             let instr = instrFromString op
             if not (checkArity instr args labels)
                 then fail $ unexpectedArityError op args labels
@@ -160,9 +165,9 @@ instance FromJSON Instruction where
                     <*> return funcs
                     <*> return labels
         parseEffectInstr op v = do
-            args <- ((v .:? "args") >>= (return . fromMaybe [])) :: Parser [VarName]
-            labels  <- ((v .:? "labels") >>= (return . fromMaybe [])) :: Parser [VarName]
-            funcs  <- ((v .:? "funcs") >>= (return . fromMaybe [])) :: Parser [VarName]
+            args  <- (v `optionalArrayField` "args") :: Parser [VarName]
+            labels  <- (v `optionalArrayField` "labels") :: Parser [VarName]
+            funcs  <- (v `optionalArrayField` "funcs") :: Parser [VarName]
             dest <- (v .:? "dest") :: Parser (Maybe VarName)
             if (op == "call") && ((length funcs) /= 1)
                 then fail $ "call op must have exactly one entry in \"funcs\""
diff --git a/tests/Main.hs b/tests/Main.hs
index 748ab7e..7bd64f8 100644
--- a/tests/Main.hs
+++ b/tests/Main.hs
@@ -72,6 +72,14 @@ testInstrs = TestCase $ do
         (eitherDecode "{\"op\": \"call\", \"type\": \"bool\", \"dest\": \"z\", \"args\": [\"a\", \"b\"], \"funcs\": []}")
         (Left "Error in $: call op must have exactly one entry in \"funcs\"" :: Either String B.Instruction)
 
+    assertEqual "parse jmp"
+        (eitherDecode "{\"op\": \"jmp\", \"labels\": [\"a\"]}")
+        (Right $ B.EffectInstr B.Jmp [] [] ["a"])
+
+    assertEqual "parse br"
+        (eitherDecode "{\"op\": \"br\", \"labels\": [\"a\", \"b\"], \"args\": [\"z\"]}")
+        (Right $ B.EffectInstr B.Br ["z"] [] ["a", "b"])
+
 tests :: Test
 tests = TestList [
         TestLabel "bril parser: type" testTypes,