diff --git a/.travis.yml b/.travis.yml
index 1ac58d82..2962e9d3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,6 +12,7 @@ rvm:
   - 2.4
   - 2.5
   - 2.6
+  - 2.7.0-preview2
   - ruby-head
   - jruby
 matrix:
diff --git a/Rakefile b/Rakefile
index ce390952..41f822cd 100644
--- a/Rakefile
+++ b/Rakefile
@@ -89,7 +89,7 @@ if defined?(Gem) and defined?(Gem::PackageTask)
 
     s.require_path = 'lib'
     s.add_development_dependency 'rake'
-    s.add_development_dependency 'test-unit', '~> 2.0'
+    s.add_development_dependency 'test-unit', '~> 3.0'
 
     s.extra_rdoc_files << 'README.md'
     s.rdoc_options <<
@@ -127,7 +127,7 @@ if defined?(Gem) and defined?(Gem::PackageTask)
 
     s.require_path = 'lib'
     s.add_development_dependency 'rake'
-    s.add_development_dependency 'test-unit', '~> 2.0'
+    s.add_development_dependency 'test-unit', '~> 3.0'
 
     s.extra_rdoc_files << 'README.md'
     s.rdoc_options <<
diff --git a/json-java.gemspec b/json-java.gemspec
old mode 100644
new mode 100755
index f3fa0c91..c99ed89d
--- a/json-java.gemspec
+++ b/json-java.gemspec
@@ -19,14 +19,14 @@ spec = Gem::Specification.new do |s|
 
     if Gem::Version.new(Gem::VERSION) >= Gem::Version.new('1.2.0') then
       s.add_development_dependency(%q<rake>, [">= 0"])
-      s.add_development_dependency(%q<test-unit>, ["~> 2.0"])
+      s.add_development_dependency(%q<test-unit>, ["~> 3.0"])
     else
       s.add_dependency(%q<rake>, [">= 0"])
-      s.add_dependency(%q<test-unit>, ["~> 2.0"])
+      s.add_dependency(%q<test-unit>, ["~> 3.0"])
     end
   else
     s.add_dependency(%q<rake>, [">= 0"])
-    s.add_dependency(%q<test-unit>, ["~> 2.0"])
+    s.add_dependency(%q<test-unit>, ["~> 3.0"])
   end
 end
 
diff --git a/json_pure.gemspec b/json_pure.gemspec
index 1dffb22a..6ee2f4da 100644
--- a/json_pure.gemspec
+++ b/json_pure.gemspec
@@ -23,16 +23,13 @@ Gem::Specification.new do |s|
 
   if s.respond_to? :specification_version then
     s.specification_version = 4
+  end
 
-    if Gem::Version.new(Gem::VERSION) >= Gem::Version.new('1.2.0') then
-      s.add_development_dependency(%q<rake>.freeze, [">= 0"])
-      s.add_development_dependency(%q<test-unit>.freeze, ["~> 2.0"])
-    else
-      s.add_dependency(%q<rake>.freeze, [">= 0"])
-      s.add_dependency(%q<test-unit>.freeze, ["~> 2.0"])
-    end
+  if s.respond_to? :add_runtime_dependency then
+    s.add_development_dependency(%q<rake>.freeze, [">= 0"])
+    s.add_development_dependency(%q<test-unit>.freeze, ["~> 3.0"])
   else
     s.add_dependency(%q<rake>.freeze, [">= 0"])
-    s.add_dependency(%q<test-unit>.freeze, ["~> 2.0"])
+    s.add_dependency(%q<test-unit>.freeze, ["~> 3.0"])
   end
 end
diff --git a/lib/json/pure/generator.rb b/lib/json/pure/generator.rb
index ccb6fe42..a1143f8b 100644
--- a/lib/json/pure/generator.rb
+++ b/lib/json/pure/generator.rb
@@ -250,7 +250,8 @@ def [](name)
           if respond_to?(name)
             __send__(name)
           else
-            instance_variable_get("@#{name}")
+            instance_variable_get("@#{name}") if
+              instance_variables.include?("@#{name}".to_sym) # avoid warning
           end
         end
 
diff --git a/lib/json/pure/parser.rb b/lib/json/pure/parser.rb
index 3a6343bc..53402964 100644
--- a/lib/json/pure/parser.rb
+++ b/lib/json/pure/parser.rb
@@ -197,7 +197,15 @@ def parse_string
       def parse_value
         case
         when scan(FLOAT)
-          @decimal_class && @decimal_class.new(self[1]) || Float(self[1])
+          if @decimal_class then
+            if @decimal_class == BigDecimal then
+              BigDecimal(self[1])
+            else
+              @decimal_class.new(self[1]) || Float(self[1])
+            end
+          else
+            Float(self[1])
+          end
         when scan(INTEGER)
           Integer(self[1])
         when scan(TRUE)