diff --git a/.bundle/config b/.bundle/config
new file mode 100644
index 0000000..4ee01a8
--- /dev/null
+++ b/.bundle/config
@@ -0,0 +1,2 @@
+---
+BUNDLE_BIN: bundler_binstubs
diff --git a/lib/cocaine/command_line.rb b/lib/cocaine/command_line.rb
index f181383..538ea61 100644
--- a/lib/cocaine/command_line.rb
+++ b/lib/cocaine/command_line.rb
@@ -41,6 +41,10 @@ def run
       output
     end
 
+    def unix?
+      (RbConfig::CONFIG['host_os'] =~ /mswin|mingw/).nil?
+    end
+
     private
 
     def with_modified_path
@@ -79,7 +83,7 @@ def interpolation(vars, key)
 
     def shell_quote(string)
       return "" if string.nil?
-      if self.class.unix?
+      if unix?
         if string.empty?
           "''"
         else
@@ -91,11 +95,7 @@ def shell_quote(string)
     end
 
     def bit_bucket
-      self.class.unix? ? "2>/dev/null" : "2>NUL"
-    end
-
-    def self.unix?
-      (RbConfig::CONFIG['host_os'] =~ /mswin|mingw/).nil?
+      unix? ? "2>/dev/null" : "2>NUL"
     end
   end
 end
diff --git a/spec/cocaine/command_line_spec.rb b/spec/cocaine/command_line_spec.rb
index ab1aa37..1aeefa2 100644
--- a/spec/cocaine/command_line_spec.rb
+++ b/spec/cocaine/command_line_spec.rb
@@ -143,17 +143,17 @@
   end
 
   it "detects that the system is unix" do
-    Cocaine::CommandLine.unix?.should be_true
+    Cocaine::CommandLine.new("convert").unix?.should be_true
   end
 
   it "detects that the system is windows" do
     on_windows!
-    Cocaine::CommandLine.unix?.should be_false
+    Cocaine::CommandLine.new("convert").unix?.should be_false
   end
 
   it "detects that the system is windows (mingw)" do
     on_mingw!
-    Cocaine::CommandLine.unix?.should be_false
+    Cocaine::CommandLine.new("convert").unix?.should be_false
   end
 
   it "logs the command to a supplied logger" do