diff --git a/lib/volumen/store.rb b/lib/volumen/store.rb
index 17edfa7..1ba6595 100644
--- a/lib/volumen/store.rb
+++ b/lib/volumen/store.rb
@@ -20,10 +20,12 @@ module Volumen
     end
 
     def all
-      mtime = Dir.exist?(@content_dir) ? File.mtime(@content_dir) : nil
-      @all = nil if mtime != @all_mtime
+      current_dir_mtime = Dir.exist?(@content_dir) ? File.mtime(@content_dir) : nil
+      current_files_mtime = newest_file_mtime
+      @all = nil if current_dir_mtime != @all_dir_mtime || current_files_mtime != @all_files_mtime
       @all ||= begin
-        @all_mtime = mtime
+        @all_dir_mtime = current_dir_mtime
+        @all_files_mtime = current_files_mtime
         markdown_files.filter_map { |path| load_post(path) }
       end
     end
@@ -79,6 +81,15 @@ module Volumen
       Dir.glob(File.join(@content_dir, "**", "*.md"))
     end
 
+    def newest_file_mtime
+      files = markdown_files
+      return nil if files.empty?
+
+      files.map { |path| File.mtime(path) }.max
+    rescue SystemCallError
+      nil
+    end
+
     def load_post(path)
       post = Post.parse(File.read(path))
       post.metadata["slug"] ||= File.basename(path, ".md")