diff --git a/includes/cache/ProcessCacheLRU.php b/includes/cache/ProcessCacheLRU.php
index f215ebd85d0..76c76f3701a 100644
--- a/includes/cache/ProcessCacheLRU.php
+++ b/includes/cache/ProcessCacheLRU.php
@@ -28,6 +28,8 @@
 class ProcessCacheLRU {
 	/** @var Array */
 	protected $cache = array(); // (key => prop => value)
+	/** @var Array */
+	protected $cacheTimes = array(); // (key => prop => UNIX timestamp)
 
 	protected $maxCacheKeys; // integer; max entries
 
@@ -44,7 +46,7 @@ class ProcessCacheLRU {
 
 	/**
 	 * Set a property field for a cache entry.
-	 * This will prune the cache if it gets too large.
+	 * This will prune the cache if it gets too large based on LRU.
 	 * If the item is already set, it will be pushed to the top of the cache.
 	 *
 	 * @param $key string
@@ -57,9 +59,12 @@ class ProcessCacheLRU {
 			$this->ping( $key ); // push to top
 		} elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
 			reset( $this->cache );
-			unset( $this->cache[key( $this->cache )] );
+			$evictKey = key( $this->cache );
+			unset( $this->cache[$evictKey] );
+			unset( $this->cacheTimes[$evictKey] );
 		}
 		$this->cache[$key][$prop] = $value;
+		$this->cacheTimes[$key][$prop] = time();
 	}
 
 	/**
@@ -67,10 +72,14 @@ class ProcessCacheLRU {
 	 *
 	 * @param $key string
 	 * @param $prop string
+	 * @param $maxAge integer Ignore items older than this many seconds (since 1.21)
 	 * @return bool
 	 */
-	public function has( $key, $prop ) {
-		return isset( $this->cache[$key][$prop] );
+	public function has( $key, $prop, $maxAge = 0 ) {
+		if ( isset( $this->cache[$key][$prop] ) ) {
+			return ( $maxAge <= 0 || ( time() - $this->cacheTimes[$key][$prop] ) <= $maxAge );
+		}
+		return false;
 	}
 
 	/**
@@ -100,9 +109,11 @@ class ProcessCacheLRU {
 	public function clear( $keys = null ) {
 		if ( $keys === null ) {
 			$this->cache = array();
+			$this->cacheTimes = array();
 		} else {
 			foreach ( (array)$keys as $key ) {
 				unset( $this->cache[$key] );
+				unset( $this->cacheTimes[$key] );
 			}
 		}
 	}
diff --git a/includes/filebackend/FileBackendStore.php b/includes/filebackend/FileBackendStore.php
index 97e49a5a092..43e6cb3ed84 100644
--- a/includes/filebackend/FileBackendStore.php
+++ b/includes/filebackend/FileBackendStore.php
@@ -48,6 +48,8 @@ abstract class FileBackendStore extends FileBackend {
 
 	protected $maxFileSize = 4294967296; // integer bytes (4GiB)
 
+	const CACHE_TTL = 10; // integer; TTL in seconds for process cache entries
+
 	/**
 	 * @see FileBackend::__construct()
 	 *
@@ -601,14 +603,15 @@ abstract class FileBackendStore extends FileBackend {
 		wfProfileIn( __METHOD__ );
 		wfProfileIn( __METHOD__ . '-' . $this->name );
 		$latest = !empty( $params['latest'] ); // use latest data?
-		if ( !$this->cheapCache->has( $path, 'stat' ) ) {
+		if ( !$this->cheapCache->has( $path, 'stat', self::CACHE_TTL ) ) {
 			$this->primeFileCache( array( $path ) ); // check persistent cache
 		}
-		if ( $this->cheapCache->has( $path, 'stat' ) ) {
+		if ( $this->cheapCache->has( $path, 'stat', self::CACHE_TTL ) ) {
 			$stat = $this->cheapCache->get( $path, 'stat' );
 			// If we want the latest data, check that this cached
-			// value was in fact fetched with the latest available data.
-			if ( !$latest || $stat['latest'] ) {
+			// value was in fact fetched with the latest available data
+			// (the process cache is ignored if it contains a negative).
+			if ( !$latest || ( is_array( $stat ) && $stat['latest'] ) ) {
 				wfProfileOut( __METHOD__ . '-' . $this->name );
 				wfProfileOut( __METHOD__ );
 				return $stat;
@@ -619,7 +622,7 @@ abstract class FileBackendStore extends FileBackend {
 		$stat = $this->doGetFileStat( $params );
 		wfProfileOut( __METHOD__ . '-miss-' . $this->name );
 		wfProfileOut( __METHOD__ . '-miss' );
-		if ( is_array( $stat ) ) { // don't cache negatives
+		if ( is_array( $stat ) ) { // file exists
 			$stat['latest'] = $latest;
 			$this->cheapCache->set( $path, 'stat', $stat );
 			$this->setFileCache( $path, $stat ); // update persistent cache
@@ -627,8 +630,11 @@ abstract class FileBackendStore extends FileBackend {
 				$this->cheapCache->set( $path, 'sha1',
 					array( 'hash' => $stat['sha1'], 'latest' => $latest ) );
 			}
-		} else {
+		} elseif ( $stat === false ) { // file does not exist
+			$this->cheapCache->set( $path, 'stat', false );
 			wfDebug( __METHOD__ . ": File $path does not exist.\n" );
+		} else { // an error occurred
+			wfDebug( __METHOD__ . ": Could not stat file $path.\n" );
 		}
 		wfProfileOut( __METHOD__ . '-' . $this->name );
 		wfProfileOut( __METHOD__ );
@@ -682,7 +688,7 @@ abstract class FileBackendStore extends FileBackend {
 		wfProfileIn( __METHOD__ );
 		wfProfileIn( __METHOD__ . '-' . $this->name );
 		$latest = !empty( $params['latest'] ); // use latest data?
-		if ( $this->cheapCache->has( $path, 'sha1' ) ) {
+		if ( $this->cheapCache->has( $path, 'sha1', self::CACHE_TTL ) ) {
 			$stat = $this->cheapCache->get( $path, 'sha1' );
 			// If we want the latest data, check that this cached
 			// value was in fact fetched with the latest available data.