diff --git a/src/Type/FileTypeMapper.php b/src/Type/FileTypeMapper.php
index 919ec6745d..4d8f49d69c 100644
--- a/src/Type/FileTypeMapper.php
+++ b/src/Type/FileTypeMapper.php
@@ -202,7 +202,7 @@ private function shouldPhpDocNodeBeCachedToDisk(PhpDocNode $phpDocNode): bool
 	private function getResolvedPhpDocMap(string $fileName): array
 	{
 		if (!isset($this->memoryCache[$fileName])) {
-			$cacheKey = sprintf('%s-phpdocstring-v4-uses', $fileName);
+			$cacheKey = sprintf('%s-phpdocstring-v5-namespace', $fileName);
 			$variableCacheKey = implode(',', array_map(static function (array $file): string {
 				return sprintf('%s-%d', $file['filename'], $file['modifiedTime']);
 			}, $this->getCachedDependentFilesWithTimestamps($fileName)));
@@ -351,8 +351,6 @@ function (\PhpParser\Node $node) use ($fileName, $lookForTrait, $traitMethodAlia
 						$phpDocMap = array_merge($phpDocMap, $traitPhpDocMap);
 					}
 					return null;
-				} elseif ($node instanceof \PhpParser\Node\Stmt\Namespace_) {
-					$namespace = (string) $node->name;
 				} elseif ($node instanceof Node\Stmt\ClassMethod) {
 					$functionName = $node->name->name;
 					if (array_key_exists($functionName, $traitMethodAliases)) {
@@ -441,7 +439,9 @@ function (\PhpParser\Node $node) use ($fileName, $lookForTrait, $traitMethodAlia
 					return self::POP_TYPE_MAP_STACK;
 				}
 
-				if ($node instanceof \PhpParser\Node\Stmt\Use_ && $node->type === \PhpParser\Node\Stmt\Use_::TYPE_NORMAL) {
+				if ($node instanceof \PhpParser\Node\Stmt\Namespace_) {
+					$namespace = (string) $node->name;
+				} elseif ($node instanceof \PhpParser\Node\Stmt\Use_ && $node->type === \PhpParser\Node\Stmt\Use_::TYPE_NORMAL) {
 					foreach ($node->uses as $use) {
 						$uses[strtolower($use->getAlias()->name)] = (string) $use->name;
 					}
diff --git a/tests/PHPStan/Rules/PhpDoc/InvalidPhpDocVarTagTypeRuleTest.php b/tests/PHPStan/Rules/PhpDoc/InvalidPhpDocVarTagTypeRuleTest.php
index b0fff26157..c47a45a87e 100644
--- a/tests/PHPStan/Rules/PhpDoc/InvalidPhpDocVarTagTypeRuleTest.php
+++ b/tests/PHPStan/Rules/PhpDoc/InvalidPhpDocVarTagTypeRuleTest.php
@@ -120,4 +120,20 @@ public function testBug4486(): void
 		]);
 	}
 
+	public function testBug4486Namespace(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-4486-ns.php'], [
+			[
+				'PHPDoc tag @var for variable $one contains unknown class ClassName1.',
+				6,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
+			[
+				'PHPDoc tag @var for variable $two contains unknown class Bug4486Namespace\ClassName1.',
+				10,
+				'Learn more at https://phpstan.org/user-guide/discovering-symbols',
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/PhpDoc/data/bug-4486-ns.php b/tests/PHPStan/Rules/PhpDoc/data/bug-4486-ns.php
new file mode 100644
index 0000000000..e914313cb2
--- /dev/null
+++ b/tests/PHPStan/Rules/PhpDoc/data/bug-4486-ns.php
@@ -0,0 +1,10 @@
+<?php
+
+/**
+ * @var ClassName1 $one
+ */
+namespace Bug4486Namespace;
+
+/**
+ * @var ClassName1 $two
+ */