diff --git a/plugin/wp-cli-login-server.php b/plugin/wp-cli-login-server.php
index 32e609b..bc90e3e 100644
--- a/plugin/wp-cli-login-server.php
+++ b/plugin/wp-cli-login-server.php
@@ -6,7 +6,7 @@
  * Author URI: https://aaemnnost.tv
  * Plugin URI: https://aaemnnost.tv/wp-cli-commands/login/
  *
- * Version: 1.5
+ * Version: 1.5.0
  */
 
 namespace WP_CLI_Login;
diff --git a/src/ServerPlugin.php b/src/ServerPlugin.php
index c20f140..ac1d009 100644
--- a/src/ServerPlugin.php
+++ b/src/ServerPlugin.php
@@ -2,7 +2,7 @@
 
 namespace WP_CLI_Login;
 
-use Composer\Semver\Semver;
+use UnexpectedValueException;
 use WP_CLI_Login\WP_CLI_Login_Server;
 
 class ServerPlugin
@@ -124,7 +124,26 @@ public function version()
      */
     public function versionSatisfies($constraints)
     {
-        return Semver::satisfies($this->version(), $constraints);
+        $constraints = is_string($constraints) ? trim($constraints) : '';
+        $version = is_string($this->version()) ? trim($this->version()) : '';
+
+        if ($constraints === '' || $version === '') {
+            // Saved installs prior to 1.5 did not persist a constraint; force reset flow.
+            return false;
+        }
+
+        try {
+            $semver = 'Composer\\Semver\\Semver';
+
+            if (!class_exists($semver)) {
+                return false;
+            }
+
+            return call_user_func([$semver, 'satisfies'], $version, $constraints);
+        } catch (UnexpectedValueException $exception) {
+            // Bail gracefully if either side is not a valid semver string.
+            return false;
+        }
     }
 
     /**
@@ -136,7 +155,7 @@ public function data()
     {
         static $loaded;
 
-        if (! $loaded) {
+        if (!$loaded) {
             $loaded = get_plugin_data($this->file);
         }
 
diff --git a/tests/unit/ServerPluginTest.php b/tests/unit/ServerPluginTest.php
new file mode 100644
index 0000000..ffc5a25
--- /dev/null
+++ b/tests/unit/ServerPluginTest.php
@@ -0,0 +1,60 @@
+<?php
+
+use PHPUnit\Framework\Assert;
+use PHPUnit\Framework\TestCase;
+use WP_CLI_Login\ServerPlugin;
+
+class ServerPluginTest extends TestCase
+{
+    private function pluginWithVersion($version)
+    {
+        return new class('dummy', $version) extends ServerPlugin {
+            private $version;
+
+            public function __construct($file, $version)
+            {
+                parent::__construct($file);
+                $this->version = $version;
+            }
+
+            public function version()
+            {
+                return $this->version;
+            }
+        };
+    }
+
+    /** @test */
+    public function empty_constraint_requires_update()
+    {
+        $plugin = $this->pluginWithVersion('1.5.0');
+
+        Assert::assertFalse($plugin->versionSatisfies(''));
+        Assert::assertFalse($plugin->versionSatisfies(null));
+    }
+
+    /** @test */
+    public function empty_version_requires_update()
+    {
+        $plugin = $this->pluginWithVersion('');
+
+        Assert::assertFalse($plugin->versionSatisfies('^1.5'));
+    }
+
+    /** @test */
+    public function invalid_constraint_requires_update()
+    {
+        $plugin = $this->pluginWithVersion('1.5.0');
+
+        Assert::assertFalse($plugin->versionSatisfies('not-a-version'));
+    }
+
+    /** @test */
+    public function valid_constraint_comparison_still_works()
+    {
+        $plugin = $this->pluginWithVersion('1.5.2');
+
+        Assert::assertTrue($plugin->versionSatisfies('^1.5'));
+        Assert::assertFalse($plugin->versionSatisfies('^2.0'));
+    }
+}