diff --git a/option/option.go b/option/option.go
index a6c78b3..d2bee36 100644
--- a/option/option.go
+++ b/option/option.go
@@ -6,6 +6,7 @@ package option
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"os/exec"
 	"strings"
@@ -53,8 +54,9 @@ func (o *Option) NewCmd(args ...string) *exec.Cmd {
 }
 
 // UpdateEnv updates the environment variable for the key name of the input.
-func (o *Option) UpdateEnv(env string) {
-	if i, exists := containsEnv(o.env, env); exists {
+func (o *Option) UpdateEnv(envKey, envValue string) {
+	env := fmt.Sprintf("%s=%s", envKey, envValue)
+	if i, exists := containsEnv(o.env, envKey); exists {
 		o.env[i] = env
 	} else {
 		o.env = append(o.env, env)
@@ -62,18 +64,16 @@ func (o *Option) UpdateEnv(env string) {
 }
 
 // DeleteEnv deletes the environment variable for the key name of the input.
-func (o *Option) DeleteEnv(env string) {
-	if i, exists := containsEnv(o.env, env); exists {
+func (o *Option) DeleteEnv(envKey string) {
+	if i, exists := containsEnv(o.env, envKey); exists {
 		o.env = append(o.env[:i], o.env[i+1:]...)
 	}
 }
 
 // containsEnv determines whether an environment variable exists.
-func containsEnv(envs []string, targetEnv string) (int, bool) {
+func containsEnv(envs []string, targetEnvKey string) (int, bool) {
 	for i, env := range envs {
-		envKey := strings.Split(env, "=")[0]
-		targetEnvKey := strings.Split(targetEnv, "=")[0]
-		if envKey == targetEnvKey {
+		if strings.Split(env, "=")[0] == targetEnvKey {
 			return i, true
 		}
 	}
diff --git a/tests/compose_build.go b/tests/compose_build.go
index 6d2a280..effe1af 100644
--- a/tests/compose_build.go
+++ b/tests/compose_build.go
@@ -45,8 +45,8 @@ func ComposeBuild(o *option.Option) {
 		})
 
 		ginkgo.It("should build services defined in the compose file specified by the COMPOSE_FILE environment variable", func() {
-			envValue := fmt.Sprintf("COMPOSE_FILE=%s", composeFilePath)
-			o.UpdateEnv(envValue)
+			envKey := "COMPOSE_FILE"
+			o.UpdateEnv(envKey, composeFilePath)
 
 			command.Run(o, "compose", "build")
 
@@ -57,7 +57,7 @@ func ComposeBuild(o *option.Option) {
 			output := command.StdoutStr(o, "run", localImages[defaultImage])
 			gomega.Expect(output).Should(gomega.Equal("Compose build test"))
 
-			o.DeleteEnv(envValue)
+			o.DeleteEnv(envKey)
 		})
 
 		ginkgo.It("should output progress in plain text format", func() {