diff --git a/builtin/assertion.go b/builtin/assertion.go
index ca290aa8..30ecfdd5 100644
--- a/builtin/assertion.go
+++ b/builtin/assertion.go
@@ -49,5 +49,8 @@ func EndsWith(t assert.TestingT, expected, actual interface{}, msgAndArgs ...int
 }
 
 func EqualLength(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool {
+	if !assert.IsType(t, 129, expected, fmt.Sprintf("expected type is not int, got %#v", expected)) {
+		return false
+	}
 	return assert.Len(t, actual, expected.(int), msgAndArgs...)
 }
diff --git a/builtin/assertion_test.go b/builtin/assertion_test.go
index 328839be..632dad30 100644
--- a/builtin/assertion_test.go
+++ b/builtin/assertion_test.go
@@ -41,3 +41,23 @@ func TestEndsWith(t *testing.T) {
 		}
 	}
 }
+
+func TestEqualLength(t *testing.T) {
+	testData := []struct {
+		raw      interface{}
+		expected int
+	}{
+		{"", 0},
+		{[]string{}, 0},
+		{map[string]interface{}{}, 0},
+		{"a", 1},
+		{[]string{"a"}, 1},
+		{map[string]interface{}{"a": 123}, 1},
+	}
+
+	for _, data := range testData {
+		if !assert.True(t, EqualLength(t, data.expected, data.raw)) {
+			t.Fail()
+		}
+	}
+}