diff --git a/src/PhpDoc/TypeNodeResolver.php b/src/PhpDoc/TypeNodeResolver.php
index dfe513aaf4..c43095a82f 100644
--- a/src/PhpDoc/TypeNodeResolver.php
+++ b/src/PhpDoc/TypeNodeResolver.php
@@ -65,6 +65,7 @@
 use PHPStan\Type\FloatType;
 use PHPStan\Type\Generic\GenericClassStringType;
 use PHPStan\Type\Generic\GenericObjectType;
+use PHPStan\Type\Generic\TemplateType;
 use PHPStan\Type\Generic\TemplateTypeVariance;
 use PHPStan\Type\Helper\GetTemplateTypeType;
 use PHPStan\Type\IntegerRangeType;
@@ -749,6 +750,9 @@ static function (string $variance): TemplateTypeVariance {
 		$mainType = $this->resolveIdentifierTypeNode($typeNode->type, $nameScope);
 		$mainTypeObjectClassNames = $mainType->getObjectClassNames();
 		if (count($mainTypeObjectClassNames) > 1) {
+			if ($mainType instanceof TemplateType) {
+				return new ErrorType();
+			}
 			throw new ShouldNotHappenException();
 		}
 		$mainTypeClassName = $mainTypeObjectClassNames[0] ?? null;
diff --git a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
index 1d2bae5a54..fc08670b02 100644
--- a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
+++ b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
@@ -1286,6 +1286,14 @@ public function testBug10302(): void
 		$this->assertNoErrors($errors);
 	}
 
+	public function testBug10509(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-10509.php');
+		$this->assertCount(2, $errors);
+		$this->assertSame('Method Bug10509\Foo::doFoo() has no return type specified.', $errors[0]->getMessage());
+		$this->assertSame('PHPDoc tag @return contains unresolvable type.', $errors[1]->getMessage());
+	}
+
 	/**
 	 * @param string[]|null $allAnalysedFiles
 	 * @return Error[]
diff --git a/tests/PHPStan/Analyser/data/bug-10509.php b/tests/PHPStan/Analyser/data/bug-10509.php
new file mode 100644
index 0000000000..cdbf76bd53
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-10509.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Bug10509;
+
+/** @template T */
+interface One
+{
+
+}
+
+/** @template T */
+interface Two
+{
+
+}
+
+/**
+ * @template T of One&Two
+ */
+class Foo
+{
+
+	/**
+	 * @return T<int>
+	 */
+	public function doFoo()
+	{
+
+	}
+
+}