diff --git a/ChangeLog.md b/ChangeLog.md
index 11f8b209..51e2cba0 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,8 @@
+# v2.5.16
+BUG FIXES
+- allow backup/restore tables and databases which contains additional special characters set, fix [938](https://github.com/Altinity/clickhouse-backup/issues/938)
+- properly restore environment variables to avoid failures in config.ValidateConfig in REST API mode, fix [940](https://github.com/Altinity/clickhouse-backup/issues/940)
+
 # v2.5.15
 IMPROVEMENTS
 - increase `s3_request_timeout_ms` (23.7+) and turn off `s3_use_adaptive_timeouts` (23.11+) when `use_embedded_backup_restore: true`
diff --git a/pkg/common/utils_test.go b/pkg/common/utils_test.go
new file mode 100644
index 00000000..0f9336f0
--- /dev/null
+++ b/pkg/common/utils_test.go
@@ -0,0 +1,19 @@
+package common
+
+import (
+	"github.com/stretchr/testify/require"
+	"net/url"
+	"testing"
+)
+
+func TestTablePathEncode(t *testing.T) {
+	r := require.New(t)
+	str := `!@#$^&*()+-=[]{}|;':\",./<>?~`
+	expected := "%21%40%23%24%5E%26%2A%28%29%2B%2D%3D%5B%5D%7B%7D%7C%3B%27%3A%5C%22%2C%2E%2F%3C%3E%3F%7E"
+
+	actual := TablePathEncode(str)
+	r.Equal(expected, actual)
+	decoded, err := url.PathUnescape(actual)
+	r.NoError(err)
+	r.Equal(str, decoded)
+}
diff --git a/pkg/config/config.go b/pkg/config/config.go
index 198854aa..2fc9fb62 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -645,9 +645,14 @@ func GetConfigPath(ctx *cli.Context) string {
 	return DefaultConfigPath
 }
 
-func OverrideEnvVars(ctx *cli.Context) map[string]string {
+type oldEnvValues struct {
+	OldValue string
+	WasPresent bool
+}
+
+func OverrideEnvVars(ctx *cli.Context) map[string]oldEnvValues {
 	env := ctx.StringSlice("env")
-	oldValues := map[string]string{}
+	oldValues := map[string]oldEnvValues{}
 	if len(env) > 0 {
 		for _, v := range env {
 			envVariable := strings.SplitN(v, "=", 2)
@@ -655,7 +660,11 @@ func OverrideEnvVars(ctx *cli.Context) map[string]string {
 				envVariable = append(envVariable, "true")
 			}
 			log.Infof("override %s=%s", envVariable[0], envVariable[1])
-			oldValues[envVariable[0]] = os.Getenv(envVariable[0])
+			oldValue, wasPresent := os.LookupEnv(envVariable[0])
+			oldValues[envVariable[0]] = oldEnvValues{
+				OldValue: oldValue,
+				WasPresent: wasPresent,
+			}
 			if err := os.Setenv(envVariable[0], envVariable[1]); err != nil {
 				log.Warnf("can't override %s=%s, error: %v", envVariable[0], envVariable[1], err)
 			}
@@ -664,10 +673,16 @@ func OverrideEnvVars(ctx *cli.Context) map[string]string {
 	return oldValues
 }
 
-func RestoreEnvVars(envVars map[string]string) {
-	for name, value := range envVars {
-		if err := os.Setenv(name, value); err != nil {
-			log.Warnf("can't restore %s=%s, error: %v", name, value, err)
+func RestoreEnvVars(envVars map[string]oldEnvValues) {
+	for name, oldEnv := range envVars {
+		if oldEnv.WasPresent {
+			if err := os.Setenv(name, oldEnv.OldValue); err != nil {
+				log.Warnf("RestoreEnvVars can't restore %s=%s, error: %v", name, oldEnv.OldValue, err)
+			}
+		} else {
+			if err := os.Unsetenv(name); err != nil {
+				log.Warnf("RestoreEnvVars can't delete %s, error: %v", name, err)
+			}
 		}
 	}
 }