diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 9e055eb2..5a8959b7 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -1257,7 +1257,7 @@ class SSH2
         $identifier = 'SSH-2.0-phpseclib_2.0';
 
         $ext = array();
-        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 df9651af..54695d5b 100644
--- a/tests/Unit/Net/SSH2Test.php
+++ b/tests/Unit/Net/SSH2Test.php
@@ -41,7 +41,7 @@ class Unit_Net_SSH2Test extends PhpseclibTestCase
         $identifier = $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);
         }