diff --git a/calculator.cabal b/calculator.cabal
--- a/calculator.cabal
+++ b/calculator.cabal
@@ -1,5 +1,5 @@
 name:                calculator
-version:             0.1.4.0
+version:             0.1.4.1
 synopsis:            A calculator that operates on string inputs
 description:         A calculator repl that processes mathematical expressions.
                      Does basic arithmetic, and provides pre-defined basic mathematical functions.
diff --git a/src/Calculator/Parser/Expr.hs b/src/Calculator/Parser/Expr.hs
--- a/src/Calculator/Parser/Expr.hs
+++ b/src/Calculator/Parser/Expr.hs
@@ -81,9 +81,12 @@
 
 parseCall :: Parser Expr
 parseCall = do
-  ident <- try (parseId <* char '(')
+  ident <- optionMaybe parseId
+  _     <- char '('
   expr  <- parseExpr
   _     <- char ')'
-  return $ Function ident expr
+  return $ case ident of
+             Nothing -> expr
+             Just s  -> Function s expr
 
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