diff --git a/vlib/v/tests/in_expression_test.v b/vlib/v/tests/in_expression_test.v
index 7f6d5d957c..3440b55d36 100644
--- a/vlib/v/tests/in_expression_test.v
+++ b/vlib/v/tests/in_expression_test.v
@@ -7,22 +7,32 @@ fn test_in_expression() {
 	arr1 := [1, 2]
 	arr2 := [0, 2]
 	arr3 := [1, 0]
+
 	a = true && 2 in arr1
 	assert a == true
 	a = false && 2 in arr1
 	assert a == false
+
 	a = true && 0 in arr2
 	assert a == true
 	a = false && 0 in arr3
 	assert a == false
+
 	a = true && 0 in arr1
 	assert a == false
 	a = true && 3 in arr1
 	assert a == false
+
 	a = true && !(2 in arr2)
 	assert a == false
 	a = true && !(3 in arr2)
 	assert a == true
+
+	a = true && (2 !in arr2)
+	assert a == false
+	a = true && (3 !in arr2)
+	assert a == true
+
 	a = 1 in arr1 && true
 	assert a == true
 	a = 1 in arr1 && false
@@ -66,10 +76,12 @@ fn test_in_expression_with_string() {
 	arr1 := ['ab', 'bc']
 	arr2 := ['', 'bc']
 	arr3 := ['ab', '']
+
 	a = true && 'bc' in arr1
 	assert a == true
 	a = false && 'bc' in arr1
 	assert a == false
+
 	a = true && '' in arr2
 	assert a == true
 	a = false && '' in arr3
@@ -78,10 +90,17 @@ fn test_in_expression_with_string() {
 	assert a == false
 	a = true && 'abc' in arr1
 	assert a == false
+
 	a = true && !('bc' in arr2)
 	assert a == false
 	a = true && !('abc' in arr2)
 	assert a == true
+
+	a = true && ('bc' !in arr2)
+	assert a == false
+	a = true && ('abc' !in arr2)
+	assert a == true
+
 	a = 'ab' in arr1 && true
 	assert a == true
 	a = 'ab' in arr1 && false
@@ -94,18 +113,27 @@ fn test_optimized_in_expression() {
 	assert a == true
 	a = false && 2 in [1, 2]
 	assert a == false
+
 	a = true && 0 in [0, 2]
 	assert a == true
 	a = false && 0 in [1, 0]
 	assert a == false
+
 	a = true && 0 in [1, 2]
 	assert a == false
 	a = true && 3 in [1, 2]
 	assert a == false
+
 	a = true && !(2 in [0, 2])
 	assert a == false
 	a = true && !(3 in [0, 2])
 	assert a == true
+
+	a = true && (2 !in [0, 2])
+	assert a == false
+	a = true && (3 !in [0, 2])
+	assert a == true
+
 	a = 1 in [1, 2] && true
 	assert a == true
 	a = 1 in [1, 2] && false
@@ -118,18 +146,27 @@ fn test_optimized_in_expression_with_enum() {
 	assert a == true
 	a = false && Colors.blue in [.green, .blue]
 	assert a == false
+
 	a = true && Colors.red in [.red, .blue]
 	assert a == true
 	a = false && Colors.red in [.green, .red]
 	assert a == false
+
 	a = true && Colors.red in [.green, .blue]
 	assert a == false
 	a = true && Colors.yellow in [.green, .blue]
 	assert a == false
+
 	a = true && !(Colors.blue in [.red, .blue])
 	assert a == false
 	a = true && !(Colors.yellow in [.red, .blue])
 	assert a == true
+
+	a = true && (Colors.blue !in [.red, .blue])
+	assert a == false
+	a = true && (Colors.yellow !in [.red, .blue])
+	assert a == true
+
 	a = Colors.green in [.green, .blue] && true
 	assert a == true
 	a = Colors.green in [.green, .blue] && false
@@ -142,18 +179,27 @@ fn test_optimized_in_expression_with_string() {
 	assert a == true
 	a = false && 'bc' in ['ab', 'bc']
 	assert a == false
+
 	a = true && '' in ['', 'bc']
 	assert a == true
 	a = false && '' in ['ab', '']
 	assert a == false
+
 	a = true && '' in ['ab', 'bc']
 	assert a == false
 	a = true && 'abc' in ['ab', 'bc']
 	assert a == false
+
 	a = true && !('bc' in ['', 'bc'])
 	assert a == false
 	a = true && !('abc' in ['', 'bc'])
 	assert a == true
+
+	a = true && ('bc' !in ['', 'bc'])
+	assert a == false
+	a = true && ('abc' !in ['', 'bc'])
+	assert a == true
+
 	a = 'ab' in ['ab', 'bc'] && true
 	assert a == true
 	a = 'ab' in ['ab', 'bc'] && false