diff --git a/spec/assertions_spec.lua b/spec/assertions_spec.lua
index c07d8d9..70a071d 100644
--- a/spec/assertions_spec.lua
+++ b/spec/assertions_spec.lua
@@ -348,27 +348,37 @@ describe("Test Assertions", function()
 
   it("Checks '_' chaining of modifiers and assertions", function()
     assert.is_string("abc")
+    assert.is_a_string("abc")
     assert.is_true(true)
     assert.is_not_string(123)
+    assert.is_not_a_string(123)
     assert.is_nil(nil)
     assert.is_not_nil({})
     assert.is_not_true(false)
     assert.is_not_false(true)
+    assert.are_the_same({a=1}, {a=1})
+    assert.are_not_the_same({a=1}, {b=1})
 
     -- verify that failing assertions actually fail
     assert.has_error(function() assert.is_string(1) end)
     assert.has_error(function() assert.is_true(false) end)
     assert.has_error(function() assert.is_not_string('string!') end)
+    assert.has_error(function() assert.is_not_a_string('string!') end)
     assert.has_error(function() assert.is_nil({}) end)
     assert.has_error(function() assert.is_not_nil(nil) end)
     assert.has_error(function() assert.is_not_true(true) end)
     assert.has_error(function() assert.is_not_false(false) end)
+    assert.has_error(function() assert.are_the_same({a=1}, {b=1}) end)
+    assert.has_a_error(function() assert.are_not_the_same({a=1}, {a=1}) end)
+    assert.has_an_error(function() assert.are_not_the_same({a=1}, {a=1}) end)
   end)
 
   it("Checks '.' chaining of modifiers and assertions", function()
     assert.is.string("abc")
+    assert.is.a.string("abc")
     assert.is.True(true)
     assert.is.Not.string(123)
+    assert.is.Not.a.string(123)
     assert.is.Nil(nil)
     assert.is.Not.Nil({})
     assert.is.Not.True(false)
@@ -376,11 +386,15 @@ describe("Test Assertions", function()
     assert.equals.Not(true, false)
     assert.equals.Not.Not(true, true)
     assert.Not.equals.Not(true, true)
+    assert.are.the.same({a=1}, {a=1})
+    assert.are.Not.the.same({a=1}, {b=1})
 
     -- verify that failing assertions actually fail
     assert.has.error(function() assert.is.string(1) end)
+    assert.has.error(function() assert.is.a.string(1) end)
     assert.has.error(function() assert.is.True(false) end)
     assert.has.error(function() assert.is.Not.string('string!') end)
+    assert.has.error(function() assert.is.Not.a.string('string!') end)
     assert.has.error(function() assert.is.Nil({}) end)
     assert.has.error(function() assert.is.Not.Nil(nil) end)
     assert.has.error(function() assert.is.Not.True(true) end)
@@ -388,6 +402,9 @@ describe("Test Assertions", function()
     assert.has.error(function() assert.equals.Not(true, true) end)
     assert.has.error(function() assert.equals.Not.Not(true, false) end)
     assert.has.error(function() assert.Not.equals.Not(true, false) end)
+    assert.has.error(function() assert.are.the.same({a=1}, {b=1}) end)
+    assert.has.a.error(function() assert.are.Not.the.same({a=1}, {a=1}) end)
+    assert.has.an.error(function() assert.are.Not.the.same({a=1}, {a=1}) end)
   end)
 
   it("Checks number of returned arguments", function()
diff --git a/src/modifiers.lua b/src/modifiers.lua
index 9493228..c74a1ef 100644
--- a/src/modifiers.lua
+++ b/src/modifiers.lua
@@ -10,6 +10,9 @@ local function is_not(state)
   return state
 end
 
+assert:register("modifier", "a", is)
+assert:register("modifier", "an", is)
+assert:register("modifier", "the", is)
 assert:register("modifier", "is", is)
 assert:register("modifier", "are", is)
 assert:register("modifier", "was", is)