diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 4c809f78..c8d1358a 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -1267,7 +1267,7 @@ class SSH2
         $identifier = 'SSH-2.0-phpseclib_2.0';
 
         $ext = [];
-        if (extension_loaded('libsodium')) {
+        if (function_exists('\\Sodium\\library_version_major')) {
             $ext[] = 'libsodium';
         }
 
diff --git a/tests/Unit/Net/SSH2Test.php b/tests/Unit/Net/SSH2Test.php
index e7057b67..b670e496 100644
--- a/tests/Unit/Net/SSH2Test.php
+++ b/tests/Unit/Net/SSH2Test.php
@@ -41,7 +41,7 @@ class Unit_Net_SSH2Test extends PhpseclibTestCase
         $identifier = self::callFunc($this->createSSHMock(), 'generate_identifier');
         $this->assertStringStartsWith('SSH-2.0-phpseclib_2.0', $identifier);
 
-        if (extension_loaded('libsodium')) {
+        if (function_exists('\\Sodium\\library_version_major')) {
             $this->assertContains('libsodium', $identifier);
         }