adding

src/filter.js

@@ -72,10 +72,7 @@ class Filter {
 	_in(value, key, result) {
 		let isValid = false
 
-		if (!result[key]) {
-			isValid = false
-		}
-
+		if (result[key]) {
 			if (Array.isArray(value)) {
 				let found = false
 
@@ -94,6 +91,7 @@ class Filter {
 					isValid = true
 				}
 			}
+		}
 
 		return isValid
 	}

test/filter.js

@@ -54,6 +54,21 @@ describe('Filter', function () {
 		assert.equal(filter.validate(data), true)
 	})
 
+	it('_in single, missing tags', function() {
+
+		const filter = new Filter({
+			tags: {
+				_in: 'monday'
+			}
+		})
+
+		const data = {
+			name: 'monday'
+		}
+
+		assert.equal(filter.validate(data), false)
+	})
+
 	it('_in array', function() {
 
 		const filter = new Filter({