diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index a99e425..ec57fa8 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -18,6 +18,8 @@ jobs:
           - '1.18'
           - '1.19'
           - '1.20'
+          - '1.21'
+          - '1.22'
     steps:
       - uses: actions/checkout@v4
         with:
diff --git a/pkg/interpreter/interpreter.go b/pkg/interpreter/interpreter.go
index fdaa9ee..f1a8f8b 100644
--- a/pkg/interpreter/interpreter.go
+++ b/pkg/interpreter/interpreter.go
@@ -149,6 +149,7 @@ func (intr *treeInterpreter) execute(node parsing.ASTNode, value interface{}, fu
 				}
 			}
 		}
+		// TODO: don't we want to return an error here ?
 		return nil, nil
 	case parsing.ASTExpRef:
 		return func(data interface{}) (interface{}, error) {
diff --git a/pkg/interpreter/interpreter_test.go b/pkg/interpreter/interpreter_test.go
index 67c6422..57e9313 100644
--- a/pkg/interpreter/interpreter_test.go
+++ b/pkg/interpreter/interpreter_test.go
@@ -185,6 +185,31 @@ func TestCanSupportProjectionsWithStructs(t *testing.T) {
 	assert.Equal([]interface{}{"first", "second", "third"}, result)
 }
 
+func TestCompareStrings(t *testing.T) {
+	assert := assert.New(t)
+	data := []string{"a", "b", "c"}
+	{
+		result, err := search(t, "@[?@ > 'a']", data)
+		assert.Nil(err)
+		assert.Equal([]interface{}{"b", "c"}, result)
+	}
+	{
+		result, err := search(t, "@[?@ >= 'b']", data)
+		assert.Nil(err)
+		assert.Equal([]interface{}{"b", "c"}, result)
+	}
+	{
+		result, err := search(t, "@[?@ < 'b']", data)
+		assert.Nil(err)
+		assert.Equal([]interface{}{"a"}, result)
+	}
+	{
+		result, err := search(t, "@[?@ <= 'b']", data)
+		assert.Nil(err)
+		assert.Equal([]interface{}{"a", "b"}, result)
+	}
+}
+
 func TestCanSupportSliceOfStructsWithFunctions(t *testing.T) {
 	assert := assert.New(t)
 	data := []scalars{{"a1", "b1"}, {"a2", "b2"}}