diff --git a/src/Reflection/Php/PhpClassReflectionExtension.php b/src/Reflection/Php/PhpClassReflectionExtension.php
index a31e70433e3..c4ad8bfbfad 100644
--- a/src/Reflection/Php/PhpClassReflectionExtension.php
+++ b/src/Reflection/Php/PhpClassReflectionExtension.php
@@ -1317,7 +1317,8 @@ private function findMethodPhpDocIncludingAncestors(
 		if ($resolved !== null) {
 			return [$resolved, $declaringClass];
 		}
-		if (!$this->stubPhpDocProvider->isKnownClass($declaringClassName)) {
+		$isKnownClass = $this->stubPhpDocProvider->isKnownClass($declaringClassName);
+		if (!$isKnownClass && !$declaringClass->isBuiltin()) {
 			return null;
 		}
 
@@ -1335,6 +1336,10 @@ private function findMethodPhpDocIncludingAncestors(
 				continue;
 			}
 
+			if (!$isKnownClass && $ancestor->isGeneric()) {
+				continue;
+			}
+
 			return [$resolved, $ancestor];
 		}
 
diff --git a/stubs/date.stub b/stubs/date.stub
index 8191057c642..3cb6da0d1de 100644
--- a/stubs/date.stub
+++ b/stubs/date.stub
@@ -41,12 +41,6 @@ interface DateTimeInterface {
 	{}
 }
 
-class DateTimeImmutable implements DateTimeInterface {
-}
-
-class DateTime implements DateTimeInterface {
-}
-
 /** @return \DateInterval&object{days:int} */
 function date_diff(\DateTimeInterface $baseObject, \DateTimeInterface $targetObject, bool $absolute = false): \DateInterval
 {}
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14632.php b/tests/PHPStan/Analyser/nsrt/bug-14632.php
new file mode 100644
index 00000000000..b7e31ae7704
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14632.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Bug14632;
+
+use DateTime;
+use DateTimeImmutable;
+use DateTimeInterface;
+use function PHPStan\Testing\assertType;
+
+function testDateTimeInterface(DateTimeInterface $a, DateTimeInterface $b): void {
+	$interval = $a->diff($b);
+	assertType('DateInterval&object{days: int}', $interval);
+	assertType('int', $interval->days);
+}
+
+function testDateTimeImmutable(DateTimeImmutable $a, DateTimeImmutable $b): void {
+	$interval = $a->diff($b);
+	assertType('DateInterval&object{days: int}', $interval);
+	assertType('int', $interval->days);
+}
+
+function testDateTime(DateTime $a, DateTime $b): void {
+	$interval = $a->diff($b);
+	assertType('DateInterval&object{days: int}', $interval);
+	assertType('int', $interval->days);
+}
diff --git a/tests/PHPStan/Analyser/nsrt/builtin-generic-ancestor-stubs.php b/tests/PHPStan/Analyser/nsrt/builtin-generic-ancestor-stubs.php
new file mode 100644
index 00000000000..0de66fc8316
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/builtin-generic-ancestor-stubs.php
@@ -0,0 +1,28 @@
+<?php // lint >= 8.4
+
+namespace BuiltinGenericAncestorStubs;
+
+use Dom\NodeList;
+use MultipleIterator;
+use SplFileObject;
+use WeakMap;
+use function PHPStan\Testing\assertType;
+
+function testSplFileObject(SplFileObject $file): void {
+	assertType('int', $file->key());
+	assertType('array|string|false', $file->current());
+}
+
+function testMultipleIterator(MultipleIterator $it): void {
+	assertType('array', $it->key());
+	assertType('array', $it->current());
+}
+
+/** @param WeakMap<object, string> $map */
+function testWeakMap(WeakMap $map): void {
+	assertType('int<0, max>', $map->count());
+}
+
+function testDomNodeList(NodeList $list): void {
+	assertType('int<0, max>', $list->count());
+}