diff --git a/internal/parse/parse.go b/internal/parse/parse.go
index c6fbc049..7b0d4844 100644
--- a/internal/parse/parse.go
+++ b/internal/parse/parse.go
@@ -5,6 +5,11 @@ import (
 	"strconv"
 )
 
+const (
+	InvalidType = "invalid type"
+	Negative    = "negative value"
+)
+
 func Int(input interface{}) (int, error) {
 	switch input := input.(type) {
 	case float64:
@@ -16,7 +21,7 @@ func Int(input interface{}) (int, error) {
 		}
 		return int(mem), nil
 	}
-	return 0, nil
+	return 0, errors.New(InvalidType)
 }
 
 func Uint(input interface{}) (uint, error) {
@@ -25,7 +30,7 @@ func Uint(input interface{}) (uint, error) {
 		return 0, err
 	}
 	if tmpInt < 0 {
-		return 0, errors.New("negative value")
+		return 0, errors.New(Negative)
 	}
 	return uint(tmpInt), nil
 }
diff --git a/internal/parse/parse_test.go b/internal/parse/parse_test.go
index f4b341b8..cbf0a1d7 100644
--- a/internal/parse/parse_test.go
+++ b/internal/parse/parse_test.go
@@ -28,6 +28,9 @@ func Test_Int(t *testing.T) {
 		{name: `string positive`,
 			input:  "1",
 			output: 1},
+		{name: `invalid type`,
+			input: interface{}(nil),
+			err:   true},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
@@ -64,6 +67,9 @@ func Test_Uint(t *testing.T) {
 		{name: `string positive`,
 			input:  "1",
 			output: 1},
+		{name: `invalid type`,
+			input: interface{}(nil),
+			err:   true},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {