diff --git a/src/Psalm/Internal/Analyzer/MethodComparator.php b/src/Psalm/Internal/Analyzer/MethodComparator.php
index e3a632692..62ff319f5 100644
--- a/src/Psalm/Internal/Analyzer/MethodComparator.php
+++ b/src/Psalm/Internal/Analyzer/MethodComparator.php
@@ -50,11 +50,13 @@ class MethodComparator
         bool $prevent_abstract_override = true,
         bool $prevent_method_signature_mismatch = true
     ): ?bool {
+        $implementer_method_id = new MethodIdentifier(
+            $implementer_classlike_storage->name,
+            strtolower($guide_method_storage->cased_name ?: '')
+        );
+
         $implementer_declaring_method_id = $codebase->methods->getDeclaringMethodId(
-            new MethodIdentifier(
-                $implementer_classlike_storage->name,
-                strtolower($guide_method_storage->cased_name ?: '')
-            )
+            $implementer_method_id
         );
 
         $cased_implementer_method_id = $implementer_classlike_storage->name . '::'
@@ -62,6 +64,11 @@ class MethodComparator
 
         $cased_guide_method_id = $guide_classlike_storage->name . '::' . $guide_method_storage->cased_name;
 
+        $codebase->methods->file_reference_provider->addMethodReferenceToClassMember(
+            strtolower((string)($implementer_declaring_method_id ?: $implementer_method_id)),
+            strtolower($guide_classlike_storage->name . '::' . $guide_method_storage->cased_name)
+        );
+
         self::checkForObviousMethodMismatches(
             $guide_classlike_storage,
             $implementer_classlike_storage,
diff --git a/tests/FileUpdates/ErrorAfterUpdateTest.php b/tests/FileUpdates/ErrorAfterUpdateTest.php
index eb45e11fc..3c026671d 100644
--- a/tests/FileUpdates/ErrorAfterUpdateTest.php
+++ b/tests/FileUpdates/ErrorAfterUpdateTest.php
@@ -907,6 +907,43 @@ class ErrorAfterUpdateTest extends \Psalm\Tests\TestCase
                 ],
                 'error_message' => 'PropertyNotSetInConstructor',
             ],
+            'invalidateChildMethodWhenSignatureChanges' => [
+                'file_stages' => [
+                    [
+                        getcwd() . DIRECTORY_SEPARATOR . 'A.php' => '<?php
+                            namespace Foo;
+
+                            class A {
+                                public function foo(string $s) : void {
+                                    echo $s;
+                                }
+                            }
+
+                            class AChild extends A {
+                                public function foo(string $s) : void {
+                                    echo $s;
+                                }
+                            }',
+                    ],
+                    [
+                        getcwd() . DIRECTORY_SEPARATOR . 'A.php' => '<?php
+                            namespace Foo;
+
+                            class A {
+                                public function foo(string $s = "") : void {
+                                    echo $s;
+                                }
+                            }
+
+                            class AChild extends A {
+                                public function foo(string $s) : void {
+                                    echo $s;
+                                }
+                            }',
+                    ],
+                ],
+                'error_message' => 'MethodSignatureMismatch',
+            ],
         ];
     }
 }