diff --git a/src/Psalm/Internal/Type/TypeTokenizer.php b/src/Psalm/Internal/Type/TypeTokenizer.php
index 59beae3cf..341f12d05 100644
--- a/src/Psalm/Internal/Type/TypeTokenizer.php
+++ b/src/Psalm/Internal/Type/TypeTokenizer.php
@@ -443,6 +443,10 @@ class TypeTokenizer
                 continue;
             }
 
+            if ($string_type_token[0] === 'func_num_args()') {
+                continue;
+            }
+
             if (isset($type_aliases[$string_type_token[0]])) {
                 $type_alias = $type_aliases[$string_type_token[0]];
 
diff --git a/tests/Template/ConditionalReturnTypeTest.php b/tests/Template/ConditionalReturnTypeTest.php
index b2a7b7864..4f5b2f3fd 100644
--- a/tests/Template/ConditionalReturnTypeTest.php
+++ b/tests/Template/ConditionalReturnTypeTest.php
@@ -461,6 +461,21 @@ class ConditionalReturnTypeTest extends TestCase
                     '$c' => 'string',
                 ]
             ],
+            'namespaceFuncNumArgs' => [
+                '<?php
+                    namespace Foo;
+
+                    /**
+                     * @return (func_num_args() is 0 ? false : string)
+                     */
+                    function zeroArgsFalseOneArgString(string $s = "") {
+                        if (func_num_args() === 0) {
+                            return false;
+                        }
+
+                        return $s;
+                    }',
+            ],
         ];
     }
 }