diff --git a/lib/fluent/plugin/in_tail.rb b/lib/fluent/plugin/in_tail.rb
index 56d1058e0e..968b352d86 100644
--- a/lib/fluent/plugin/in_tail.rb
+++ b/lib/fluent/plugin/in_tail.rb
@@ -184,7 +184,7 @@ def expand_paths
         path = date.strftime(path)
         if path.include?('*')
           paths += Dir.glob(path).select { |p|
-            if File.readable?(p)
+            if File.readable?(p) && !File.directory?(p)
               true
             else
               log.warn "#{p} unreadable. It is excluded and would be examined next time."
diff --git a/test/plugin/data/log/foo/bar2 b/test/plugin/data/log/foo/bar2
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/test/plugin/test_in_tail.rb b/test/plugin/test_in_tail.rb
index 83851ad360..98dbf12278 100644
--- a/test/plugin/test_in_tail.rb
+++ b/test/plugin/test_in_tail.rb
@@ -847,6 +847,25 @@ def test_expand_paths
       plugin = create_driver(exclude_config, false).instance
       assert_equal EX_PATHS - [EX_PATHS.last], plugin.expand_paths.sort
     end
+
+    def test_log_file_without_extension
+      expected_files = [
+        'test/plugin/data/log/bar',
+        'test/plugin/data/log/foo/bar.log',
+        'test/plugin/data/log/foo/bar2',
+        'test/plugin/data/log/test.log'
+      ]
+
+      config = config_element("", "", {
+        "tag" => "tail",
+        "path" => "test/plugin/data/log/**/*",
+        "format" => "none",
+        "pos_file" => "#{TMP_DIR}/tail.pos"
+      })
+
+      plugin = create_driver(config, false).instance
+      assert_equal expected_files, plugin.expand_paths.sort
+    end
   end
 
   def test_z_refresh_watchers