diff --git a/internal/configuration/sources/env/firewall.go b/internal/configuration/sources/env/firewall.go
index 2ae038af..9b8d3c44 100644
--- a/internal/configuration/sources/env/firewall.go
+++ b/internal/configuration/sources/env/firewall.go
@@ -65,7 +65,7 @@ func stringsToPorts(ss []string) (ports []uint16, err error) {
 		if err != nil {
 			return nil, fmt.Errorf("%w: %s: %s",
 				ErrPortParsing, s, err)
-		} else if port < 1 || port > 2^16 {
+		} else if port < 1 || port > 65535 {
 			return nil, fmt.Errorf("%w: must be between 1 and 65535: %d",
 				ErrPortValue, port)
 		}
diff --git a/internal/configuration/sources/env/serverselection.go b/internal/configuration/sources/env/serverselection.go
index cfdd8537..1b3f9d3f 100644
--- a/internal/configuration/sources/env/serverselection.go
+++ b/internal/configuration/sources/env/serverselection.go
@@ -49,8 +49,8 @@ func (r *Reader) readServerSelection(vpnProvider, vpnType string) (
 			if err != nil {
 				return ss, fmt.Errorf("%w: %s",
 					ErrServerNumberNotValid, numberString)
-			} else if number < 0 || number > 2^16 {
-				return ss, fmt.Errorf("%w: %d must be between 0 and 2^16",
+			} else if number < 0 || number > 65535 {
+				return ss, fmt.Errorf("%w: %d must be between 0 and 65535",
 					ErrServerNumberNotValid, number)
 			}
 			numbers[i] = uint16(number)