diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1bf0f2e..95f44f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,7 +20,9 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 
 - language literals were not properly unescaped during Turtle parsing
 - `RDF.Literal.new/1` can take decimals and infers the datatype `xsd:decimal` 
-  correctly  
+  correctly
+- `true` and `false` with capital letters are no longer valid `RDF.Boolean`s 
+  following the XSD specification; the same applies for booleans in Turtle
 
 
 [Compare v0.6.0...HEAD](https://github.com/marcelotto/rdf-ex/compare/v0.6.0...HEAD)
diff --git a/lib/rdf/datatypes/boolean.ex b/lib/rdf/datatypes/boolean.ex
index e28415f..0825ceb 100644
--- a/lib/rdf/datatypes/boolean.ex
+++ b/lib/rdf/datatypes/boolean.ex
@@ -14,10 +14,10 @@ defmodule RDF.Boolean do
   def convert(value, _) when is_boolean(value), do: value
 
   def convert(value, opts) when is_binary(value) do
-    with normalized_value = String.downcase(value) do
+    with value do
       cond do
-        normalized_value in ~W[true 1]  -> true
-        normalized_value in ~W[false 0] -> false
+        value in ~W[true 1]  -> true
+        value in ~W[false 0] -> false
         true ->
           super(value, opts)
       end
diff --git a/test/unit/datatypes/boolean_test.exs b/test/unit/datatypes/boolean_test.exs
index 458ed4d..c37b96d 100644
--- a/test/unit/datatypes/boolean_test.exs
+++ b/test/unit/datatypes/boolean_test.exs
@@ -8,12 +8,10 @@ defmodule RDF.BooleanTest do
       1       => { true  , nil     , "true"  },
       "true"  => { true  , nil     , "true"  },
       "false" => { false , nil     , "false" },
-      "tRuE"  => { true  , "tRuE"  , "true"  },
-      "FaLsE" => { false , "FaLsE" , "false" },
       "0"     => { false , "0"     , "false" },
       "1"     => { true  , "1"     , "true"  },
     },
-    invalid: ~w(foo 10) ++ [42, 3.14, "true false", "true foo"]
+    invalid: ~w(foo 10) ++ [42, 3.14, "tRuE", "FaLsE", "true false", "true foo"]
 
   import RDF.Sigils
 
@@ -53,11 +51,9 @@ defmodule RDF.BooleanTest do
 
     test "casting a string with a value from the lexical value space of xsd:boolean" do
       assert RDF.string("true")  |> RDF.Boolean.cast() == RDF.true
-      assert RDF.string("tRuE")  |> RDF.Boolean.cast() == RDF.true
       assert RDF.string("1")     |> RDF.Boolean.cast() == RDF.true
 
       assert RDF.string("false") |> RDF.Boolean.cast() == RDF.false
-      assert RDF.string("FaLsE") |> RDF.Boolean.cast() == RDF.false
       assert RDF.string("0")     |> RDF.Boolean.cast() == RDF.false
     end
 
diff --git a/test/unit/equality_test.exs b/test/unit/equality_test.exs
index bf9be0f..9750550 100644
--- a/test/unit/equality_test.exs
+++ b/test/unit/equality_test.exs
@@ -109,13 +109,13 @@ defmodule RDF.EqualityTest do
       {RDF.boolean("foo"), RDF.boolean("bar")},
     ]
     @value_equal_booleans [
-      {RDF.true,       RDF.boolean("TRUE")},
-      {RDF.boolean(1), RDF.true},
+      {RDF.true,       RDF.boolean("1")},
+      {RDF.boolean(0), RDF.false},
       # invalid literals
       {RDF.boolean("foo"), RDF.boolean("foo")},
     ]
     @value_unequal_booleans [
-      {RDF.true,       RDF.boolean("FALSE")},
+      {RDF.true,       RDF.boolean("false")},
       {RDF.boolean(0), RDF.true},
       # invalid literals
       {RDF.boolean("foo"), RDF.boolean("bar")},
diff --git a/test/unit/turtle_encoder_test.exs b/test/unit/turtle_encoder_test.exs
index ea6a70b..fbba658 100644
--- a/test/unit/turtle_encoder_test.exs
+++ b/test/unit/turtle_encoder_test.exs
@@ -534,11 +534,9 @@ defmodule RDF.Turtle.EncoderTest do
       [
         {true,    "true ."},
         {"true",  "true ."},
-        {"TrUe",  "true ."},
         {"1",     "true ."},
         {false,   "false ."},
         {"false", "false ."},
-        {"FaLsE", "false ."},
         {"0",     "false ."},
       ]
       |> Enum.each(fn {value, output} ->
@@ -550,7 +548,9 @@ defmodule RDF.Turtle.EncoderTest do
     test "invalid booleans" do
       [
         {"string", ~s{"string"^^<http://www.w3.org/2001/XMLSchema#boolean>}},
-        {"42",     ~s{"42"^^<http://www.w3.org/2001/XMLSchema#boolean>}}
+        {"42",     ~s{"42"^^<http://www.w3.org/2001/XMLSchema#boolean>}},
+        {"TrUe",   ~s{"TrUe"^^<http://www.w3.org/2001/XMLSchema#boolean>}},
+        {"FaLsE",  ~s{"FaLsE"^^<http://www.w3.org/2001/XMLSchema#boolean>}},
       ]
       |> Enum.each(fn {value, output} ->
           Graph.new({EX.S, EX.p, RDF.Boolean.new(value)})