diff --git a/.travis.yml b/.travis.yml
index 91f7f93..53998d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,7 +20,7 @@ install:
   - luarocks install luacov-coveralls
 
 script:
-  - luacheck --std max+busted *.lua spec
+  - luacheck --no-unused-args --std max+busted *.lua spec
   - busted --verbose --coverage
 
 after_success:
diff --git a/middleclass.lua b/middleclass.lua
index 1c793e7..90fda19 100644
--- a/middleclass.lua
+++ b/middleclass.lua
@@ -138,8 +138,8 @@ local DefaultMixin = {
 
       local subclass = _createClass(name, self)
 
-      for name, f in pairs(self.__instanceDict) do
-        _propagateInstanceMethod(subclass, name, f)
+      for methodName, f in pairs(self.__instanceDict) do
+        _propagateInstanceMethod(subclass, methodName, f)
       end
       subclass.initialize = function(instance, ...) return self.initialize(instance, ...) end
 
diff --git a/spec/class_spec.lua b/spec/class_spec.lua
index 5924437..144cb9f 100644
--- a/spec/class_spec.lua
+++ b/spec/class_spec.lua
@@ -1,5 +1,4 @@
 local class = require 'middleclass'
-local Object = class.Object
 
 describe('class()', function()
 
diff --git a/spec/default_methods_spec.lua b/spec/default_methods_spec.lua
index d7c8e86..81602f0 100644
--- a/spec/default_methods_spec.lua
+++ b/spec/default_methods_spec.lua
@@ -204,7 +204,7 @@ describe('Default methods', function()
         describe('A ' .. theType, function()
 
           local f1 = function() return Object.isSubclassOf(Object, primitive) end
-          local f2 = function() return Object.isSubclassOf(primitive, o) end
+          local f2 = function() return Object.isSubclassOf(primitive, Object:new()) end
           local f3 = function() return Object.isSubclassOf(primitive, primitive) end
 
           describe('does not throw errors', function()
diff --git a/spec/metamethods_lua_5_2.lua b/spec/metamethods_lua_5_2.lua
index 7b119b1..2ea6c9b 100644
--- a/spec/metamethods_lua_5_2.lua
+++ b/spec/metamethods_lua_5_2.lua
@@ -6,7 +6,7 @@ local before_each = require('busted').before_each
 local assert = require('busted').assert
 
 describe('Lua 5.2 Metamethods', function()
-  local Vector, a, b
+  local Vector, v
   before_each(function()
     Vector= class('Vector')
     function Vector.initialize(a,x,y,z) a.x, a.y, a.z = x,y,z end
@@ -16,69 +16,67 @@ describe('Lua 5.2 Metamethods', function()
     function Vector.__pairs(a)
       local t = {x=a.x,y=a.y,z=a.z}
       return coroutine.wrap(function()
-        for k,v in pairs(t) do
-          coroutine.yield(k,v)
+        for k,val in pairs(t) do
+          coroutine.yield(k,val)
         end
       end)
     end
     function Vector.__ipairs(a)
       local t = {a.x,a.y,a.z}
       return coroutine.wrap(function()
-        for k,v in ipairs(t) do
-          coroutine.yield(k,v)
+        for k,val in ipairs(t) do
+          coroutine.yield(k,val)
         end
       end)
     end
 
-    a = Vector:new(1,2,3)
-    b = Vector:new(2,4,6)
+    v = Vector:new(1,2,3)
   end)
 
   it('implements __len', function()
-    assert.equal(#a, 3)
+    assert.equal(#v, 3)
   end)
 
   it('implements __pairs',function()
     local output = {}
-    for k,v in pairs(a) do
-      output[k] = v
+    for k,val in pairs(v) do
+      output[k] = val
     end
     assert.are.same(output,{x=1,y=2,z=3})
   end)
 
   it('implements __ipairs',function()
     local output = {}
-    for _,i in ipairs(a) do
+    for _,i in ipairs(v) do
       output[#output+1] = i
     end
     assert.are.same(output,{1,2,3})
   end)
 
   describe('Inherited Metamethods', function()
-    local Vector2, c, d
+    local Vector2, v2
     before_each(function()
       Vector2= class('Vector2', Vector)
       function Vector2:initialize(x,y,z) Vector.initialize(self,x,y,z) end
 
-      c = Vector2:new(1,2,3)
-      d = Vector2:new(2,4,6)
+      v2 = Vector2:new(1,2,3)
     end)
 
     it('implements __len', function()
-      assert.equal(#c, 3)
+      assert.equal(#v2, 3)
     end)
 
     it('implements __pairs',function()
       local output = {}
-      for k,v in pairs(c) do
-        output[k] = v
+      for k,val in pairs(v2) do
+        output[k] = val
       end
       assert.are.same(output,{x=1,y=2,z=3})
     end)
 
     it('implements __ipairs',function()
       local output = {}
-      for _,i in ipairs(c) do
+      for _,i in ipairs(v2) do
         output[#output+1] = i
       end
       assert.are.same(output,{1,2,3})
diff --git a/spec/metamethods_lua_5_3.lua b/spec/metamethods_lua_5_3.lua
index 8d926a3..e74f6d7 100644
--- a/spec/metamethods_lua_5_3.lua
+++ b/spec/metamethods_lua_5_3.lua
@@ -6,7 +6,7 @@ local before_each = require('busted').before_each
 local assert = require('busted').assert
 
 describe('Lua 5.3 Metamethods', function()
-  local Vector, a, b, last_gc
+  local Vector, v, last_gc
   before_each(function()
     Vector= class('Vector')
     function Vector.initialize(a,x,y,z) a.x, a.y, a.z = x,y,z end
@@ -14,8 +14,8 @@ describe('Lua 5.3 Metamethods', function()
     function Vector.__pairs(a)
       local t = {x=a.x,y=a.y,z=a.z}
       return coroutine.wrap(function()
-        for k,v in pairs(t) do
-          coroutine.yield(k,v)
+        for k,val in pairs(t) do
+          coroutine.yield(k,val)
         end
       end)
     end
@@ -29,80 +29,78 @@ describe('Lua 5.3 Metamethods', function()
     function Vector.__shr(a,n)  return a.class:new(a.x >> n, a.y >> n, a.z >> n) end
     function Vector.__bnot(a)   return a.class:new(~a.x, ~a.y, ~a.z) end
 
-    a = Vector:new(1,2,3)
-    b = Vector:new(2,4,6)
+    v = Vector:new(1,2,3)
   end)
 
   it('implements __gc', function()
     collectgarbage()
-    a = nil
+    v = nil
     collectgarbage()
     assert.are.same(last_gc, {"Vector",1,2,3})
   end)
 
   it('implements __band', function()
-    assert.equal(a & 1, Vector(1,0,1))
+    assert.equal(v & 1, Vector(1,0,1))
   end)
 
   it('implements __bor', function()
-    assert.equal(a | 0, Vector(1,2,3))
+    assert.equal(v | 0, Vector(1,2,3))
   end)
 
   it('implements __bxor', function()
-    assert.equal(a | 1, Vector(1,3,3))
+    assert.equal(v | 1, Vector(1,3,3))
   end)
 
   it('implements __shl', function()
-    assert.equal(a << 1, Vector(2,4,6))
+    assert.equal(v << 1, Vector(2,4,6))
   end)
 
   it('implements __shr', function()
-    assert.equal(a >> 1, Vector(0,1,1))
+    assert.equal(v >> 1, Vector(0,1,1))
   end)
 
   it('implements __bnot', function()
-    assert.equal(~a, Vector(-2,-3,-4))
+    assert.equal(~v, Vector(-2,-3,-4))
   end)
 
   describe('Inherited Metamethods', function()
-    local Vector2, c, d
+    local Vector2, v2
     before_each(function()
       Vector2= class('Vector2', Vector)
       function Vector2:initialize(x,y,z) Vector.initialize(self,x,y,z) end
 
-      c = Vector2:new(1,2,3)
-      d = Vector2:new(2,4,6)
+      v2 = Vector2:new(1,2,3)
     end)
 
     it('implements __gc', function()
       collectgarbage()
-      c = nil
+      v2 = nil
       collectgarbage()
       assert.are.same(last_gc, {"Vector2",1,2,3})
     end)
 
     it('implements __band', function()
-      assert.equal(c & 1, Vector2(1,0,1))
+      assert.equal(v2 & 1, Vector2(1,0,1))
     end)
 
     it('implements __bor', function()
-      assert.equal(c | 0, Vector2(1,2,3))
+      assert.equal(v2 | 0, Vector2(1,2,3))
     end)
 
     it('implements __bxor', function()
-      assert.equal(c | 1, Vector2(1,3,3))
+      assert.equal(v2 | 1, Vector2(1,3,3))
     end)
 
     it('implements __shl', function()
-      assert.equal(c << 1, Vector2(2,4,6))
+      assert.equal(v2 << 1, Vector2(2,4,6))
     end)
 
     it('implements __shr', function()
-      assert.equal(c >> 1, Vector2(0,1,1))
+      assert.equal(v2 >> 1, Vector2(0,1,1))
     end)
 
     it('implements __bnot', function()
-      assert.equal(~c, Vector2(-2,-3,-4))
+      assert.equal(~v2, Vector2(-2,-3,-4))
     end)
   end)
 end)
diff --git a/spec/metamethods_spec.lua b/spec/metamethods_spec.lua
index 6e8277e..73bf883 100644
--- a/spec/metamethods_spec.lua
+++ b/spec/metamethods_spec.lua
@@ -1,5 +1,4 @@
 local class = require 'middleclass'
-local Object = class.Object
 
 local function is_lua_5_2_compatible()
   return type(rawlen) == 'function'
@@ -19,7 +18,7 @@ end
 
 describe('Metamethods', function()
   describe('Custom Metamethods', function()
-    local Vector, a, b
+    local Vector, v, w
     before_each(function()
       Vector= class('Vector')
       function Vector.initialize(a,x,y,z) a.x, a.y, a.z = x,y,z end
@@ -43,62 +42,62 @@ describe('Metamethods', function()
       Vector.__metatable = "metatable of a vector"
       Vector.__mode = "k"
 
-      a = Vector:new(1,2,3)
-      b = Vector:new(2,4,6)
+      v = Vector:new(1,2,3)
+      w = Vector:new(2,4,6)
     end)
 
     it('implements __tostring', function()
-      assert.equal(tostring(a), "Vector[1,2,3]")
+      assert.equal(tostring(v), "Vector[1,2,3]")
     end)
 
     it('implements __eq', function()
-      assert.equal(a, a)
+      assert.equal(v, v)
     end)
 
     it('implements __lt', function()
-      assert.is_true(a < b)
+      assert.is_true(v < w)
     end)
 
     it('implements __le', function()
-      assert.is_true(a <= b)
+      assert.is_true(v <= w)
     end)
 
     it('implements __add', function()
-      assert.equal(a+b, Vector(3,6,9))
+      assert.equal(v+w, Vector(3,6,9))
     end)
 
     it('implements __sub', function()
-      assert.equal(b-a, Vector(1,2,3))
+      assert.equal(w-v, Vector(1,2,3))
     end)
 
     it('implements __div', function()
-      assert.equal(b/2, Vector(1,2,3))
+      assert.equal(w/2, Vector(1,2,3))
     end)
 
     it('implements __concat', function()
-      assert.equal(a..b, 28)
+      assert.equal(v..w, 28)
     end)
 
     it('implements __call', function()
-      assert.equal(a(), math.sqrt(14))
+      assert.equal(v(), math.sqrt(14))
     end)
 
     it('implements __pow', function()
-      assert.equal(a^b, Vector(0,0,0))
+      assert.equal(v^w, Vector(0,0,0))
     end)
 
     it('implements __mul', function()
-      assert.equal(4*a, Vector(4,8,12))
+      assert.equal(4*v, Vector(4,8,12))
     end)
 
     it('implements __metatable', function()
-      assert.equal("metatable of a vector", getmetatable(a))
+      assert.equal("metatable of a vector", getmetatable(v))
     end)
 
     it('implements __mode', function()
-      a[{}] = true
+      v[{}] = true
       collectgarbage()
-      for k in pairs(a) do assert.not_table(k) end
+      for k in pairs(v) do assert.not_table(k) end
     end)
 
     --[[
@@ -108,97 +107,97 @@ describe('Metamethods', function()
     --]]
 
     describe('Inherited Metamethods', function()
-      local Vector2, c, d
+      local Vector2, v2, w2
       before_each(function()
         Vector2= class('Vector2', Vector)
         function Vector2:initialize(x,y,z) Vector.initialize(self,x,y,z) end
 
-        c = Vector2:new(1,2,3)
-        d = Vector2:new(2,4,6)
+        v2 = Vector2:new(1,2,3)
+        w2 = Vector2:new(2,4,6)
       end)
 
       it('implements __tostring', function()
-        assert.equal(tostring(c), "Vector2[1,2,3]")
+        assert.equal(tostring(v2), "Vector2[1,2,3]")
       end)
 
       it('implements __eq', function()
-        assert.equal(c, c)
+        assert.equal(v2, v2)
       end)
 
       it('implements __lt', function()
-        assert.is_true(c < d)
+        assert.is_true(v2 < w2)
       end)
 
       it('implements __le', function()
-        assert.is_true(c <= d)
+        assert.is_true(v2 <= w2)
       end)
 
       it('implements __add', function()
-        assert.equal(c+d, Vector2(3,6,9))
+        assert.equal(v2+w2, Vector2(3,6,9))
       end)
 
       it('implements __sub', function()
-        assert.equal(d-c, Vector2(1,2,3))
+        assert.equal(w2-v2, Vector2(1,2,3))
       end)
 
       it('implements __div', function()
-        assert.equal(d/2, Vector2(1,2,3))
+        assert.equal(w2/2, Vector2(1,2,3))
       end)
 
       it('implements __concat', function()
-        assert.equal(c..d, 28)
+        assert.equal(v2..w2, 28)
       end)
 
       it('implements __call', function()
-        assert.equal(c(), math.sqrt(14))
+        assert.equal(v2(), math.sqrt(14))
       end)
 
       it('implements __pow', function()
-        assert.equal(c^d, Vector2(0,0,0))
+        assert.equal(v2^w2, Vector2(0,0,0))
       end)
 
       it('implements __mul', function()
-        assert.equal(4*c, Vector2(4,8,12))
+        assert.equal(4*v2, Vector2(4,8,12))
       end)
 
       it('implements __metatable', function()
-        assert.equal("metatable of a vector", getmetatable(c))
+        assert.equal("metatable of a vector", getmetatable(v2))
       end)
 
       it('implements __mode', function()
-        c[{}] = true
+        v2[{}] = true
         collectgarbage()
-        for k in pairs(c) do assert.not_table(k) end
+        for k in pairs(v2) do assert.not_table(k) end
       end)
 
       it('allows inheriting further', function()
         local Vector3 = class('Vector3', Vector2)
-        local e = Vector3(1,2,3)
-        local f = Vector3(3,4,5)
-        assert.equal(e+f, Vector3(4,6,8))
+        local v3 = Vector3(1,2,3)
+        local w3 = Vector3(3,4,5)
+        assert.equal(v3+w3, Vector3(4,6,8))
       end)
 
       describe('Updates', function()
         it('overrides __add', function()
           Vector2.__add = function(a, b) return Vector.__add(a, b)/2 end
-          assert.equal(c+d, Vector2(1.5,3,4.5))
+          assert.equal(v2+w2, Vector2(1.5,3,4.5))
         end)
 
         it('updates __add', function()
           Vector.__add = Vector.__sub
-          assert.equal(c+d, Vector2(-1,-2,-3))
+          assert.equal(v2+w2, Vector2(-1,-2,-3))
         end)
 
         it('does not update __add after overriding', function()
           Vector2.__add = function(a, b) return Vector.__add(a, b)/2 end
           Vector.__add = Vector.__sub
-          assert.equal(c+d, Vector2(-0.5,-1,-1.5))
+          assert.equal(v2+w2, Vector2(-0.5,-1,-1.5))
         end)
 
         it('reverts __add override', function()
           Vector2.__add = function(a, b) return Vector.__add(a, b)/2 end
           Vector2.__add = nil
-          assert.equal(c+d, Vector2(3,6,9))
+          assert.equal(v2+w2, Vector2(3,6,9))
         end)
       end)
     end)