diff --git a/opts/env.go b/opts/env.go
index e6ddd73309..d21c8ccbef 100644
--- a/opts/env.go
+++ b/opts/env.go
@@ -1,46 +1,30 @@
 package opts
 
 import (
-	"fmt"
 	"os"
-	"runtime"
 	"strings"
+
+	"github.com/pkg/errors"
 )
 
 // ValidateEnv validates an environment variable and returns it.
-// If no value is specified, it returns the current value using os.Getenv.
+// If no value is specified, it obtains its value from the current environment
 //
 // As on ParseEnvFile and related to #16585, environment variable names
-// are not validate what so ever, it's up to application inside docker
+// are not validated, and it's up to the application inside the container
 // to validate them or not.
 //
 // The only validation here is to check if name is empty, per #25099
 func ValidateEnv(val string) (string, error) {
-	arr := strings.Split(val, "=")
+	arr := strings.SplitN(val, "=", 2)
 	if arr[0] == "" {
-		return "", fmt.Errorf("invalid environment variable: %s", val)
+		return "", errors.New("invalid environment variable: " + val)
 	}
 	if len(arr) > 1 {
 		return val, nil
 	}
-	if !doesEnvExist(val) {
-		return val, nil
+	if envVal, ok := os.LookupEnv(arr[0]); ok {
+		return arr[0] + "=" + envVal, nil
 	}
-	return fmt.Sprintf("%s=%s", val, os.Getenv(val)), nil
-}
-
-func doesEnvExist(name string) bool {
-	for _, entry := range os.Environ() {
-		parts := strings.SplitN(entry, "=", 2)
-		if runtime.GOOS == "windows" {
-			// Environment variable are case-insensitive on Windows. PaTh, path and PATH are equivalent.
-			if strings.EqualFold(parts[0], name) {
-				return true
-			}
-		}
-		if parts[0] == name {
-			return true
-		}
-	}
-	return false
+	return val, nil
 }
diff --git a/opts/env_test.go b/opts/env_test.go
index 6f6c7a7a29..3561ceb314 100644
--- a/opts/env_test.go
+++ b/opts/env_test.go
@@ -5,38 +5,115 @@ import (
 	"os"
 	"runtime"
 	"testing"
+
+	"gotest.tools/v3/assert"
 )
 
 func TestValidateEnv(t *testing.T) {
-	valids := map[string]string{
-		"a":                   "a",
-		"something":           "something",
-		"_=a":                 "_=a",
-		"env1=value1":         "env1=value1",
-		"_env1=value1":        "_env1=value1",
-		"env2=value2=value3":  "env2=value2=value3",
-		"env3=abc!qwe":        "env3=abc!qwe",
-		"env_4=value 4":       "env_4=value 4",
-		"PATH":                fmt.Sprintf("PATH=%v", os.Getenv("PATH")),
-		"PATH=something":      "PATH=something",
-		"asd!qwe":             "asd!qwe",
-		"1asd":                "1asd",
-		"123":                 "123",
-		"some space":          "some space",
-		"  some space before": "  some space before",
-		"some space after  ":  "some space after  ",
+	type testCase struct {
+		value    string
+		expected string
+		err      error
 	}
-	// Environment variables are case in-sensitive on Windows
+	tests := []testCase{
+		{
+			value:    "a",
+			expected: "a",
+		},
+		{
+			value:    "something",
+			expected: "something",
+		},
+		{
+			value:    "_=a",
+			expected: "_=a",
+		},
+		{
+			value:    "env1=value1",
+			expected: "env1=value1",
+		},
+		{
+			value:    "_env1=value1",
+			expected: "_env1=value1",
+		},
+		{
+			value:    "env2=value2=value3",
+			expected: "env2=value2=value3",
+		},
+		{
+			value:    "env3=abc!qwe",
+			expected: "env3=abc!qwe",
+		},
+		{
+			value:    "env_4=value 4",
+			expected: "env_4=value 4",
+		},
+		{
+			value:    "PATH",
+			expected: fmt.Sprintf("PATH=%v", os.Getenv("PATH")),
+		},
+		{
+			value: "=a",
+			err:   fmt.Errorf("invalid environment variable: =a"),
+		},
+		{
+			value:    "PATH=",
+			expected: "PATH=",
+		},
+		{
+			value:    "PATH=something",
+			expected: "PATH=something",
+		},
+		{
+			value:    "asd!qwe",
+			expected: "asd!qwe",
+		},
+		{
+			value:    "1asd",
+			expected: "1asd",
+		},
+		{
+			value:    "123",
+			expected: "123",
+		},
+		{
+			value:    "some space",
+			expected: "some space",
+		},
+		{
+			value:    "  some space before",
+			expected: "  some space before",
+		},
+		{
+			value:    "some space after  ",
+			expected: "some space after  ",
+		},
+		{
+			value: "=",
+			err:   fmt.Errorf("invalid environment variable: ="),
+		},
+	}
+
 	if runtime.GOOS == "windows" {
-		valids["PaTh"] = fmt.Sprintf("PaTh=%v", os.Getenv("PATH"))
+		// Environment variables are case in-sensitive on Windows
+		tests = append(tests, testCase{
+			value:    "PaTh",
+			expected: fmt.Sprintf("PaTh=%v", os.Getenv("PATH")),
+			err:      nil,
+		})
 	}
-	for value, expected := range valids {
-		actual, err := ValidateEnv(value)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if actual != expected {
-			t.Fatalf("Expected [%v], got [%v]", expected, actual)
-		}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.value, func(t *testing.T) {
+			actual, err := ValidateEnv(tc.value)
+
+			if tc.err == nil {
+				assert.NilError(t, err)
+			} else {
+				assert.Error(t, err, tc.err.Error())
+			}
+			assert.Equal(t, actual, tc.expected)
+		})
 	}
 }