diff --git a/src/main/wacc/parser.scala b/src/main/wacc/parser.scala
index 8141a4c..71198b2 100644
--- a/src/main/wacc/parser.scala
+++ b/src/main/wacc/parser.scala
@@ -13,6 +13,7 @@ import cats.data.NonEmptyList
 import parsley.errors.DefaultErrorBuilder
 import parsley.errors.ErrorBuilder
 import parsley.errors.tokenextractors.LexToken
+import parsley.character.char
 
 object parser {
   import lexer.implicits.implicitSymbol
@@ -49,6 +50,9 @@ object parser {
     case Expr
     case Pair
 
+  val _parensCheck =
+    char('(').verifiedExplain("functions can only be called using 'call' keyword")
+
   implicit val builder: ErrorBuilder[String] = new DefaultErrorBuilder with LexToken {
     def tokens = errTokens
   }
@@ -67,8 +71,8 @@ object parser {
         GreaterEq from ">="
       ) +:
       SOps(InfixL)(
-        (Add from "+").label("binary operator"),
-        (Sub from "-").label("binary operator")
+        ((Add from "+").label("binary operator") | _parensCheck),
+        ((Sub from "-").label("binary operator") | _parensCheck)
       ) +:
       SOps(InfixL)(Mul from "*", Div from "/", Mod from "%") +:
       SOps(Prefix)(