diff --git a/src/cbor/decoder.cr b/src/cbor/decoder.cr
index 12ad40a..c64d726 100644
--- a/src/cbor/decoder.cr
+++ b/src/cbor/decoder.cr
@@ -47,6 +47,14 @@ class CBOR::Decoder
     end
   end
 
+  def read_simple_value : Bool?
+    case token = @current_token
+    when Token::SimpleValueT
+      finish_token!
+      token.value.to_t
+    end
+  end
+
   def read_string : String
     case token = @current_token
     when Token::StringT
diff --git a/src/cbor/from_cbor.cr b/src/cbor/from_cbor.cr
index 32d5453..8aa080b 100644
--- a/src/cbor/from_cbor.cr
+++ b/src/cbor/from_cbor.cr
@@ -218,13 +218,22 @@ end
 def Union.new(decoder : CBOR::Decoder)
   {% begin %}
     case decoder.current_token
-    {% if T.includes? Nil %}
+    {% if T.includes? Nil || T.includes? Bool %}
     when CBOR::Token::SimpleValueT
-      return decoder.read_nil
-    {% end %}
-    {% if T.includes? Bool %}
-    when CBOR::Token::SimpleValueT
-      return decoder.read_bool
+      # This value could be either a boolean or nil.
+      value = decoder.read_simple_value
+      case value
+      {% if T.includes? Bool %}
+      when Bool
+        return value
+      {% end %}
+      {% if T.includes? Nil %}
+      when Nil
+        return nil
+      {% end %}
+      else
+        raise "value is neither Bool or Nil"
+      end
     {% end %}
     {% if T.includes? String %}
     when CBOR::Token::StringT