diff --git a/smnp/ast/node/list.py b/smnp/ast/node/list.py
index b59a1d0..ed77d62 100644
--- a/smnp/ast/node/list.py
+++ b/smnp/ast/node/list.py
@@ -1,5 +1,6 @@
 from smnp.ast.node.iterable import abstractIterableParser
 from smnp.ast.node.model import Node
+from smnp.ast.parser import Parser
 from smnp.token.type import TokenType
 
 
@@ -14,5 +15,5 @@ def ListParser(input):
         List,
         TokenType.OPEN_SQUARE,
         TokenType.CLOSE_SQUARE,
-        ExpressionParser
+        Parser.doAssert(ExpressionParser, "expression")
     )(input)
diff --git a/smnp/ast/node/map.py b/smnp/ast/node/map.py
index d96182e..47784dd 100644
--- a/smnp/ast/node/map.py
+++ b/smnp/ast/node/map.py
@@ -36,8 +36,8 @@ def MapParser(input):
 
     mapEntryParser = Parser.allOf(
         keyParser,
-        Parser.terminal(TokenType.ARROW, createNode=Operator.withValue),
-        valueParser,
+        Parser.terminal(TokenType.ARROW, createNode=Operator.withValue, doAssert=True),
+        Parser.doAssert(valueParser, "expression"),
         createNode=MapEntry.withValues
     )