diff --git a/OpenRA.Game/Support/ConditionExpression.cs b/OpenRA.Game/Support/ConditionExpression.cs
index 9ffd48ab29..03af2d6f47 100644
--- a/OpenRA.Game/Support/ConditionExpression.cs
+++ b/OpenRA.Game/Support/ConditionExpression.cs
@@ -641,12 +641,7 @@ namespace OpenRA.Support
 
 		static Expression AsBool(Expression expression)
 		{
-			return Expressions.Expression.GreaterThan(expression, Zero);
-		}
-
-		static Expression AsNegBool(Expression expression)
-		{
-			return Expressions.Expression.LessThanOrEqual(expression, Zero);
+			return Expressions.Expression.NotEqual(expression, Zero);
 		}
 
 		static Expression IfThenElse(Expression test, Expression ifTrue, Expression ifFalse)
@@ -757,10 +752,7 @@ namespace OpenRA.Support
 
 						case TokenType.Not:
 						{
-							if (ast.PeekType() == ExpressionType.Bool)
-								ast.Push(Expressions.Expression.Not(ast.Pop(ExpressionType.Bool)));
-							else
-								ast.Push(AsNegBool(ast.Pop(ExpressionType.Int)));
+							ast.Push(Expressions.Expression.Not(ast.Pop(ExpressionType.Bool)));
 							continue;
 						}
 
diff --git a/OpenRA.Test/OpenRA.Game/ConditionExpressionTest.cs b/OpenRA.Test/OpenRA.Game/ConditionExpressionTest.cs
index 66cc5faea7..14cb0475ee 100644
--- a/OpenRA.Test/OpenRA.Game/ConditionExpressionTest.cs
+++ b/OpenRA.Test/OpenRA.Game/ConditionExpressionTest.cs
@@ -163,7 +163,7 @@ namespace OpenRA.Test
 			AssertValue("!1", 0);
 			AssertValue("!5", 0);
 			AssertValue("!!5", 1);
-			AssertValue("!-5", 1);
+			AssertValue("!-5", 0);
 		}
 
 		[TestCase(TestName = "Relation operations")]