diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 84f0c6e..d428385 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -112,13 +112,13 @@ jobs:
         run: composer install --no-progress --prefer-dist --optimize-autoloader
 
       - name: Security check for locked dependencies
-        uses: symfonycorp/security-checker-action@v2
+        uses: symfonycorp/security-checker-action@v3
 
       - name: Update Composer dependencies
         run: composer update --no-progress --prefer-dist --optimize-autoloader
 
       - name: Security check for updated dependencies
-        uses: symfonycorp/security-checker-action@v2
+        uses: symfonycorp/security-checker-action@v3
 
   sanity-check:
     name: Sanity checks
diff --git a/src/Assert.php b/src/Assert.php
index b33a655..a1565a7 100644
--- a/src/Assert.php
+++ b/src/Assert.php
@@ -5,6 +5,7 @@
 namespace SimpleSAML\Assert;
 
 use BadMethodCallException;
+use DateTime;
 use DateTimeImmutable;
 use InvalidArgumentException;
 use Throwable;
@@ -347,15 +348,19 @@ public static function __callStatic(string $name, array $arguments): void
             // Putting Webmozart first, since the most calls will be to their native assertions
             if (method_exists(Webmozart::class, $name)) {
                 call_user_func_array([Webmozart::class, $name], $arguments);
-            } else if (method_exists(static::class, $name)) {
+            } elseif (method_exists(static::class, $name)) {
                 call_user_func_array([static::class, $name], $arguments);
-            } else if (preg_match('/^nullOr(.*)$/i', $name, $matches)) {
+            } elseif (preg_match('/^nullOr(.*)$/i', $name, $matches)) {
                 $method = lcfirst($matches[1]);
-                if (method_exists(static::class, $method)) {
-                    call_user_func_array([static::class, 'nullOr'], [$method, $arguments]);
+                if (method_exists(Webmozart::class, $method)) {
+                    call_user_func_array([static::class, 'nullOr'], [[Webmozart::class, $method], $arguments]);
+                } elseif (method_exists(static::class, $method)) {
+                    call_user_func_array([static::class, 'nullOr'], [[static::class, $method], $arguments]);
+                } else {
+                    throw new BadMethodCallException(sprintf("Assertion named `%s` does not exists.", $method));
                 }
             } else {
-                throw new BadMethodCallException();
+                throw new BadMethodCallException(sprintf("Assertion named `%s` does not exists.", $name));
             }
         } catch (InvalidArgumentException $e) {
             throw new $exception($e->getMessage());
@@ -375,14 +380,14 @@ public static function __callStatic(string $name, array $arguments): void
     /**
      * nullOr* for our custom assertions
      *
-     * @param string $method
+     * @param callable $method
      * @param array $arguments
      * @return void
      */
-    private static function nullOr(string $method, array $arguments): void
+    private static function nullOr(array $method, array $arguments): void
     {
         $value = reset($arguments);
-        ($value === null) || call_user_func_array([static::class, $method], $arguments);
+        ($value === null) || call_user_func_array($method, $arguments);
     }
 
 
diff --git a/tests/Assert/AssertTest.php b/tests/Assert/AssertTest.php
index 1f4f61a..3afc0bc 100644
--- a/tests/Assert/AssertTest.php
+++ b/tests/Assert/AssertTest.php
@@ -61,6 +61,15 @@ public function testUnknownAssertionRaisesBadMethodCallException(): void
     }
 
 
+    /**
+     */
+    public function testUnknownNullOrAssertionRaisesBadMethodCallException(): void
+    {
+        $this->expectException(BadMethodCallException::class);
+        Assert::nullOrThisAssertionDoesNotExist('a', 'b', LogicException::class);
+    }
+
+
     /**
      * @doesNotPerformAssertions
      */
@@ -278,7 +287,7 @@ public function testValidNCName(): void
     public function testInvalidQName(): void
     {
         $this->expectException(AssertionFailedException::class);
-        Assert::validQName('test');
+        Assert::validQName('1test');
     }