diff --git a/app/Services/Auth/ApiGuard.php b/app/Services/Auth/ApiGuard.php
index fbc9991d6..17aca366f 100644
--- a/app/Services/Auth/ApiGuard.php
+++ b/app/Services/Auth/ApiGuard.php
@@ -25,10 +25,13 @@ public function user()
         $user = null;
 
         $token = $this->getTokenForRequest();
+        $email = $this->request->getUser();
 
-        if (!empty($token)) {
+        // Check the encoding bcause a user can put anything into the string and cause
+        // a server/database error with weird strings.
+        if (!empty($token) && !empty($email) && mb_detect_encoding($email) !== false) {
             $user = $this->provider->retrieveByCredentials(
-                ['email' => strtolower($this->request->getUser())]
+                ['email' => strtolower($email)]
             );
         }
 
diff --git a/tests/php/Services/Auth/ApiGuardTest.php b/tests/php/Services/Auth/ApiGuardTest.php
index 898331380..17e2b316b 100644
--- a/tests/php/Services/Auth/ApiGuardTest.php
+++ b/tests/php/Services/Auth/ApiGuardTest.php
@@ -92,6 +92,25 @@ public function testEmailCaseInsensitive()
         $response->assertStatus(200);
     }
 
+    public function testEmailEncoding()
+    {
+        $token = ApiTokenTest::create([
+            // 'test_token', hashed with 4 rounds as defined in phpunit.xml
+            'hash' => '$2y$04$9Ncj6qJVqenJ13VtdtV5yOca8rQyN1UwATdGpAQ80FeRjS67.Efaq',
+        ]);
+
+        $token->owner->email = 'test@test.com';
+        $token->owner->save();
+
+        // The request would produce a 500 error if the string was not escaped properly.
+        // The string is from a real request that we observed.
+        $response = $this->json('GET', '/api/v1/users', [], [
+            'PHP_AUTH_USER' => "\x81\x5C\x91\xE7=e\x17\xDD\x9Do\x19lgF",
+            'PHP_AUTH_PW' => 'test_token',
+        ]);
+        $response->assertStatus(401);
+    }
+
     public function testTouchToken()
     {
         $token = ApiTokenTest::create([