diff --git a/ext/java/org/jruby/ext/stringio/StringIO.java b/ext/java/org/jruby/ext/stringio/StringIO.java
index a3acdc5..4bbe4af 100644
--- a/ext/java/org/jruby/ext/stringio/StringIO.java
+++ b/ext/java/org/jruby/ext/stringio/StringIO.java
@@ -83,6 +83,9 @@ public static RubyClass createStringIOClass(final Ruby runtime) {
         RubyClass stringIOClass = runtime.defineClass(
                 "StringIO", runtime.getObject(), StringIO::new);
 
+        RubyString version = RubyString.newString(runtime, "3.0.8");
+        stringIOClass.defineConstant("VERSION", version);
+
         stringIOClass.defineAnnotatedMethods(StringIO.class);
         stringIOClass.includeModule(runtime.getEnumerable());
 
diff --git a/rakelib/version.rake b/rakelib/version.rake
index f1a7c2a..1f6d605 100644
--- a/rakelib/version.rake
+++ b/rakelib/version.rake
@@ -1,15 +1,14 @@
 class << (helper = Bundler::GemHelper.instance)
-  SOURCE_PATH = "ext/stringio/stringio.c"
+  C_SOURCE_PATH = "ext/stringio/stringio.c"
+  JAVA_SOURCE_PATH = "ext/java/org/jruby/ext/stringio/StringIO.java"
   def update_source_version
-    path = SOURCE_PATH
-    File.open(path, "r+b") do |f|
-      d = f.read
-      if d.sub!(/^#define\s+STRINGIO_VERSION\s+\K".*"/) {version.to_s.dump}
-        f.rewind
-        f.truncate(0)
-        f.print(d)
-      end
-    end
+    c_source = File.read(C_SOURCE_PATH)
+    c_source.sub!(/^#define\s+STRINGIO_VERSION\s+\K".*"/) {version.to_s.dump}
+    File.write(C_SOURCE_PATH, c_source)
+
+    java_source = File.read(JAVA_SOURCE_PATH)
+    java_source.sub!(/version = RubyString\.newString\(runtime, \K".*"/) {version.to_s.dump}
+    File.write(JAVA_SOURCE_PATH, java_source)
   end
 
   def commit_bump
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index 246f107..d2d96c5 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -14,6 +14,10 @@ def open_file(content)
 
   include TestEOF::Seek
 
+  def test_version
+    assert_kind_of(String, StringIO::VERSION)
+  end
+
   def test_initialize
     assert_kind_of StringIO, StringIO.new
     assert_kind_of StringIO, StringIO.new('str')