diff --git a/spec/ameba/glob_utils_spec.cr b/spec/ameba/glob_utils_spec.cr
index 41309195..153b7909 100644
--- a/spec/ameba/glob_utils_spec.cr
+++ b/spec/ameba/glob_utils_spec.cr
@@ -1,11 +1,7 @@
 require "../spec_helper"
 
 module Ameba
-  struct GlobUtilsClass
-    include GlobUtils
-  end
-
-  subject = GlobUtilsClass.new
+  subject = GlobUtils
   current_file_basename = File.basename(__FILE__)
   current_file_path = "spec/ameba/#{current_file_basename}"
 
@@ -45,6 +41,12 @@ module Ameba
         subject.expand(["**/#{current_file_basename}", "**/#{current_file_basename}"])
           .should eq [current_file_path]
       end
+
+      it "does not list folders" do
+        subject.expand(["**/*"]).each do |path|
+          fail "#{path.inspect} should be a file" unless File.file?(path)
+        end
+      end
     end
   end
 end
diff --git a/src/ameba/glob_utils.cr b/src/ameba/glob_utils.cr
index 71cd0cb5..63dd67cc 100644
--- a/src/ameba/glob_utils.cr
+++ b/src/ameba/glob_utils.cr
@@ -1,6 +1,8 @@
 module Ameba
   # Helper module that is utilizes helpers for working with globs.
   module GlobUtils
+    extend self
+
     # Returns all files that match specified globs.
     # Globs can have wildcards or be rejected:
     #
@@ -20,10 +22,13 @@ module Ameba
     # expand(["spec/*.cr", "src"]) # => all files in src folder + first level specs
     # ```
     def expand(globs)
-      globs.flat_map do |glob|
-        glob += "/**/*.cr" if File.directory?(glob)
-        Dir[glob]
-      end.uniq!
+      globs
+        .flat_map do |glob|
+          glob += "/**/*.cr" if File.directory?(glob)
+          Dir[glob]
+        end
+        .uniq!
+        .select! { |path| File.file?(path) }
     end
 
     private def rejected_globs(globs)