diff --git a/schala-lang/language/src/parsing.rs b/schala-lang/language/src/parsing.rs
index 5fa1524..04ee0b1 100644
--- a/schala-lang/language/src/parsing.rs
+++ b/schala-lang/language/src/parsing.rs
@@ -620,7 +620,7 @@ impl Parser {
   fn call_expr(&mut self) -> ParseResult<Expression> {
     let mut expr = self.index_expr()?;
     while let LParen = self.token_handler.peek_kind() {
-      let arguments = delimited!(self, LParen, expression, Comma, RParen);
+      let arguments = delimited!(self, LParen, invocation_argument, Comma, RParen);
       let arguments = arguments.into_iter().map(|s| Meta::new(s)).collect();
       expr = Expression(ExpressionKind::Call { f: bx!(expr.into()), arguments }, None); //TODO none is incorrect
     }
@@ -629,8 +629,28 @@ impl Parser {
   }
 
   #[recursive_descent_method]
-  fn invocation_argument(&mut self) -> ParseResult<InvocationExpression> {
-    panic!()
+  fn invocation_argument(&mut self) -> ParseResult<InvocationArgument> {
+    Ok(match self.token_handler.peek_kind() {
+      Underscore => {
+        self.token_handler.next();
+        InvocationArgument::Ignored
+      },
+      Identifier(s) => {
+        self.token_handler.next();
+        match self.token_handler.peek_kind() {
+          Operator(ref op) if **op == "=" => {
+            self.token_handler.next();
+            let expr = self.expression()?;
+            InvocationArgument::Keyword { name: s.clone(), expr }
+          },
+          _ => {
+            let expr = self.expression()?;
+            InvocationArgument::Positional(expr)
+          }
+        }
+      },
+      _ => InvocationArgument::Positional(self.expression()?)
+    })
   }
 
   #[recursive_descent_method]
@@ -1159,7 +1179,7 @@ mod parse_tests {
   use super::tokenize;
   use super::ParseResult;
   use crate::builtin::{PrefixOp, BinOp};
-  use crate::ast::{AST, Meta, Expression, Statement, IfExpressionBody, Discriminator, Pattern, PatternLiteral, TypeBody, Enumerator, ForBody};
+  use crate::ast::{AST, Meta, Expression, Statement, IfExpressionBody, Discriminator, Pattern, PatternLiteral, TypeBody, Enumerator, ForBody, InvocationArgument};
   use super::Statement::*;
   use super::Declaration::*;
   use super::Signature;
@@ -1207,6 +1227,10 @@ mod parse_tests {
     };
   }
 
+  macro_rules! inv {
+    ($expr_type:expr) => { Meta::new(InvocationArgument::Positional(ex!($expr_type))) }
+  }
+
   macro_rules! binexp {
     ($op:expr, $lhs:expr, $rhs:expr) => { BinExp(BinOp::from_sigil($op), bx!(Expression($lhs, None).into()), bx!(Expression($rhs, None).into())) }
   }
@@ -1339,7 +1363,7 @@ mod parse_tests {
     parse_test!("oi()", AST(vec![exst!(Call { f: bx!(ex!(m val!("oi"))), arguments: vec![] })]));
     parse_test!("oi(a, 2 + 2)", AST(vec![exst!(Call
     { f: bx!(ex!(m val!("oi"))),
-      arguments: vec![ex!(val!("a")).into(), ex!(binexp!("+", NatLiteral(2), NatLiteral(2))).into()]
+      arguments: vec![inv!(val!("a")).into(), inv!(binexp!("+", NatLiteral(2), NatLiteral(2))).into()]
     })]));
     parse_error!("a(b,,c)");
 
@@ -1602,7 +1626,7 @@ fn a(x) {
           type_anno: None,
           body: vec![exst!(s "y")] }
         )),
-        arguments: vec![ex!(NatLiteral(1)).into()] })]));
+        arguments: vec![inv!(NatLiteral(1)).into()] })]));
 
     parse_test_wrap_ast! {
       r#"\(x: Int): String { "q" }"#,
@@ -1644,7 +1668,7 @@ fn a(x) {
         exst! {
           Call {
             f: bx!(ex!(m Call { f: bx!(ex!(m val!("wahoo"))), arguments: vec![] })),
-            arguments: vec![ex!(s "3").into()],
+            arguments: vec![inv!(NatLiteral(3)).into()],
           }
         }
       ])
diff --git a/schala-lang/language/src/reduced_ast.rs b/schala-lang/language/src/reduced_ast.rs
index 022b15a..1ae39a2 100644
--- a/schala-lang/language/src/reduced_ast.rs
+++ b/schala-lang/language/src/reduced_ast.rs
@@ -118,6 +118,17 @@ fn reduce_block(block: &Block, symbol_table: &SymbolTable) -> Vec<Stmt> {
   block.iter().map(|stmt| stmt.node().reduce(symbol_table)).collect()
 }
 
+impl InvocationArgument {
+  fn reduce(&self, symbol_table: &SymbolTable) -> Expr {
+    use crate::ast::InvocationArgument::*;
+    match self {
+      Positional(ex) => ex.reduce(symbol_table),
+      Keyword { .. } => Expr::UnimplementedSigilValue,
+      Ignored => Expr::UnimplementedSigilValue,
+    }
+  }
+}
+
 impl Expression {
   fn reduce(&self, symbol_table: &SymbolTable) -> Expr {
     use crate::ast::ExpressionKind::*;
diff --git a/schala-lang/language/src/typechecking.rs b/schala-lang/language/src/typechecking.rs
index d97898b..3f1d595 100644
--- a/schala-lang/language/src/typechecking.rs
+++ b/schala-lang/language/src/typechecking.rs
@@ -289,6 +289,14 @@ impl<'a> TypeContext<'a> {
     Ok(ty!(Unit))
   }
 
+  fn invoc(&mut self, invoc: &InvocationArgument) -> InferResult<Type> {
+    use InvocationArgument::*;
+    match invoc {
+      Positional(expr) => self.expr(expr),
+      _ => Ok(ty!(Nat)) //TODO this is wrong
+    }
+  }
+
   fn expr(&mut self, expr: &Expression) -> InferResult<Type> {
     match expr {
       Expression(expr_type, Some(anno)) => {
@@ -376,9 +384,9 @@ impl<'a> TypeContext<'a> {
     Ok(ty!(argument_types, ret_type))
   }
 
-  fn call(&mut self, f: &Expression, args: &Vec<Meta<Expression>>) -> InferResult<Type> {
+  fn call(&mut self, f: &Expression, args: &Vec<Meta<InvocationArgument>>) -> InferResult<Type> {
     let tf = self.expr(f)?;
-    let arg_types: InferResult<Vec<Type>> = args.iter().map(|ex| self.expr(ex.node())).collect();
+    let arg_types: InferResult<Vec<Type>> = args.iter().map(|ex| self.invoc(ex.node())).collect();
     let arg_types = arg_types?;
     self.handle_apply(tf, arg_types)
   }