diff --git a/src/Psalm/Checker/Statements/Expression/CallChecker.php b/src/Psalm/Checker/Statements/Expression/CallChecker.php
index 609a9bf1b..3230ba3b3 100644
--- a/src/Psalm/Checker/Statements/Expression/CallChecker.php
+++ b/src/Psalm/Checker/Statements/Expression/CallChecker.php
@@ -1481,7 +1481,7 @@ class CallChecker
                                 }
                             }
 
-                            if (!$has_valid_method) {
+                            if (!$has_valid_method && !$param_type->hasString() && !$param_type->hasArray()) {
                                 if (MethodChecker::checkMethodExists(
                                     $project_checker,
                                     $non_existent_method_ids[0],
@@ -1493,7 +1493,7 @@ class CallChecker
                                 }
                             }
                         } else {
-                            if (self::checkFunctionExists(
+                            if (!$param_type->hasString() && !$param_type->hasArray() && self::checkFunctionExists(
                                 $statements_checker,
                                 $function_id,
                                 $code_location,
diff --git a/tests/ClosureTest.php b/tests/ClosureTest.php
index 5ca8639a6..c8ec7b140 100644
--- a/tests/ClosureTest.php
+++ b/tests/ClosureTest.php
@@ -206,6 +206,15 @@ class ClosureTest extends TestCase
 
                     new A([new A, new A]);',
             ],
+            'possiblyUndefinedFunction' => [
+                '<?php
+                      /**
+                       * @param string|callable $middlewareOrPath
+                       */
+                      function pipe($middlewareOrPath, ?callable $middleware = null): void {  }
+
+                    pipe("zzzz", function() : void {});',
+            ],
         ];
     }