diff --git a/boost.api.inc b/boost.api.inc
index 5fd192537a5694b3ad7848dbd8603148bd1aa411..d16d53151438e175052bbb91b30908cf447dfea2 100644
--- a/boost.api.inc
+++ b/boost.api.inc
@@ -60,7 +60,9 @@ function boost_is_cached($path) {
  */
 function boost_cache_clear_all() {
   clearstatcache();
-  return _boost_rmdir_rf(boost_cache_directory());
+  if (($cache_dir = boost_cache_directory()) && file_exists($cache_dir)) {
+    return _boost_rmdir_rf($cache_dir);
+  }
 }
 
 /**
@@ -68,7 +70,9 @@ function boost_cache_clear_all() {
  */
 function boost_cache_expire_all() {
   clearstatcache();
-  _boost_rmdir_rf(boost_cache_directory(), 'boost_file_is_expired');
+  if (($cache_dir = boost_cache_directory()) && file_exists($cache_dir)) {
+    _boost_rmdir_rf($cache_dir, 'boost_file_is_expired');
+  }
   return TRUE;
 }