diff --git a/smnp/ast/node/expression.py b/smnp/ast/node/expression.py
index 243337f..4d0ea0d 100644
--- a/smnp/ast/node/expression.py
+++ b/smnp/ast/node/expression.py
@@ -43,9 +43,9 @@ def ExpressionParser(input):
     ifElseExpression = Parser.allOf(
         expr4,
         Parser.terminal(TokenType.IF),
-        expr4,
-        Parser.terminal(TokenType.ELSE),
-        expr4,
+        Parser.doAssert(expr4, "expression"),
+        Parser.terminal(TokenType.ELSE, doAssert=True),
+        Parser.doAssert(expr4, "expression"),
         createNode=lambda ifNode, _, condition, __, elseNode: IfElse.createNode(ifNode, condition, elseNode)
     )
 
diff --git a/smnp/ast/node/identifier.py b/smnp/ast/node/identifier.py
index e3a0e6c..97f0c5f 100644
--- a/smnp/ast/node/identifier.py
+++ b/smnp/ast/node/identifier.py
@@ -56,14 +56,14 @@ def IdentifierLiteralParser(input):
 def IdentifierParser(input):
     functionCallParser = Parser.allOf(
         IdentifierLiteralParser,
-        abstractIterableParser(ArgumentsList, TokenType.OPEN_PAREN, TokenType.CLOSE_PAREN, ExpressionParser),
+        abstractIterableParser(ArgumentsList, TokenType.OPEN_PAREN, TokenType.CLOSE_PAREN, Parser.doAssert(ExpressionParser, "expression")),
         createNode=lambda name, arguments: FunctionCall.withChildren(name, arguments)
     )
 
     assignmentParser = Parser.allOf(
         IdentifierLiteralParser,
         Parser.terminal(TokenType.ASSIGN, createNode=Operator.withValue),
-        ExpressionParser,
+        Parser.doAssert(ExpressionParser, "expression"),
         createNode=lambda identifier, assign, expr: Assignment.withValues(identifier, assign, expr)
     )