diff --git a/schala-lang/language/src/ast.rs b/schala-lang/language/src/ast.rs
index 9f47ee0..d440a82 100644
--- a/schala-lang/language/src/ast.rs
+++ b/schala-lang/language/src/ast.rs
@@ -125,7 +125,7 @@ pub enum ExpressionKind {
   },
   Call {
     f: Box<Meta<Expression>>,
-    arguments: Vec<Meta<Expression>>,
+    arguments: Vec<Meta<InvocationArgument>>,
   },
   Index {
     indexee: Box<Meta<Expression>>,
@@ -151,6 +151,16 @@ pub enum ExpressionKind {
   ListLiteral(Vec<Meta<Expression>>),
 }
 
+#[derive(Debug, PartialEq, Clone)]
+pub enum InvocationArgument {
+  Positional(Expression),
+  Keyword {
+    name: Rc<String>,
+    expr: Expression,
+  },
+  Ignored
+}
+
 #[derive(Debug, PartialEq, Clone)]
 pub enum Discriminator {
   Simple(Expression),
diff --git a/schala-lang/language/src/parsing.rs b/schala-lang/language/src/parsing.rs
index dace2c2..5fa1524 100644
--- a/schala-lang/language/src/parsing.rs
+++ b/schala-lang/language/src/parsing.rs
@@ -69,8 +69,9 @@
 //! precedence_expr := prefix_expr
 //! prefix_expr := prefix_op call_expr
 //! prefix_op := "+" | "-" | "!" | "~"
-//! call_expr := index_expr ( "(" expr_list ")" )* | ε
-//! expr_list := expression ("," expression)* | ε
+//! call_expr := index_expr ( "(" invocation_list ")" )* | ε
+//! invocation_list := invocation_argument ("," invocation_argument)* | ε
+//! invocation_argument := expression | IDENTIFIER "=" expression | "_"
 //! index_expr := primary ( "[" (expression ("," (expression)* | ε) "]" )*
 //! primary := literal | paren_expr | if_expr | for_expr | while_expr | identifier_expr | lambda_expr | anonymous_struct | list_expr
 //! expr_or_block := "{" (statement delimiter)* "}" | expr
@@ -627,6 +628,11 @@ impl Parser {
     Ok(expr)
   }
 
+  #[recursive_descent_method]
+  fn invocation_argument(&mut self) -> ParseResult<InvocationExpression> {
+    panic!()
+  }
+
   #[recursive_descent_method]
   fn index_expr(&mut self) -> ParseResult<Expression> {
     let primary = self.primary()?;