diff --git a/packages/filterparser/src/parseFilter.ts b/packages/filterparser/src/parseFilter.ts
index 7afa36ebd..9d170a6f5 100644
--- a/packages/filterparser/src/parseFilter.ts
+++ b/packages/filterparser/src/parseFilter.ts
@@ -223,10 +223,10 @@ const createParser = (filterType: FilterType) => {
     null: () => word('NULL').map(unaryCondition('isNull')),
     empty: () => word('EMPTY').map(unaryCondition('isEmpty')),
     notEmpty: r => r.not.then(r.empty).map(unaryCondition('isNotEmpty')),
-    true: () => P.regexp(/true/i).map(binaryFixedValueCondition(1)),
-    false: () => P.regexp(/false/i).map(binaryFixedValueCondition(0)),
-    trueNum: () => word('1').map(binaryFixedValueCondition(1)),
-    falseNum: () => word('0').map(binaryFixedValueCondition(0)),
+    true: () => P.regexp(/true/i).map(binaryFixedValueCondition('1')),
+    false: () => P.regexp(/false/i).map(binaryFixedValueCondition('0')),
+    trueNum: () => word('1').map(binaryFixedValueCondition('1')),
+    falseNum: () => word('0').map(binaryFixedValueCondition('0')),
 
     this: () => word('THIS'),
     last: () => word('LAST'),