diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/ArgumentAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/ArgumentAnalyzer.php
index b47953b10..9eca88ea3 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/ArgumentAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/ArgumentAnalyzer.php
@@ -459,7 +459,9 @@ class ArgumentAnalyzer
                     ) {
                         $arg_type = clone $unpacked_atomic_array->properties[$unpacked_argument_offset];
                     } else {
-                        $arg_type = Type::getMixed();
+                        $arg_type = $function_param->is_optional
+                            ? ($function_param->default_type ?: Type::getMixed())
+                            : Type::getMixed();
                     }
                 } elseif ($unpacked_atomic_array instanceof Type\Atomic\TList) {
                     $arg_type = $unpacked_atomic_array->type_param;
diff --git a/tests/ArgTest.php b/tests/ArgTest.php
index 3d565def7..3682133bc 100644
--- a/tests/ArgTest.php
+++ b/tests/ArgTest.php
@@ -268,6 +268,11 @@ class ArgTest extends TestCase
                 [],
                 '8.0'
             ],
+            'variadicArgsOptional' => [
+                '<?php
+                    bar(...["aaaaa"]);
+                    function bar(string $p1, int $p3 = 10) : void {}'
+            ],
         ];
     }