diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 6ae9e805b5..4c135ef8c2 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -11,6 +11,8 @@
 
 **********************************************************************/
 
+#define STRINGIO_VERSION "0.0.2"
+
 #include "ruby.h"
 #include "ruby/io.h"
 #include "ruby/encoding.h"
@@ -1629,6 +1631,8 @@ Init_stringio(void)
 #undef rb_intern
     VALUE StringIO = rb_define_class("StringIO", rb_cData);
 
+    rb_define_const(StringIO, "VERSION", rb_str_new_cstr(STRINGIO_VERSION));
+
     rb_include_module(StringIO, rb_mEnumerable);
     rb_define_alloc_func(StringIO, strio_s_allocate);
     rb_define_singleton_method(StringIO, "new", strio_s_new, -1);
diff --git a/ext/stringio/stringio.gemspec b/ext/stringio/stringio.gemspec
index df1d468f93..c0258bac5e 100644
--- a/ext/stringio/stringio.gemspec
+++ b/ext/stringio/stringio.gemspec
@@ -3,9 +3,18 @@
 # stub: stringio 0.0.0 ruby lib
 # stub: extconf.rb
 
+source_version = ["", "ext/stringio/"].find do |dir|
+  begin
+    File.open(File.join(__dir__, "#{dir}stringio.c")) {|f|
+      f.gets("\n#define STRINGIO_VERSION ")
+      f.gets[/\s*(".+")/, 1].undump
+    }
+  rescue Errno::ENOENT
+  end
+end
 Gem::Specification.new do |s|
   s.name = "stringio".freeze
-  s.version = "0.0.2"
+  s.version = source_version
 
   s.required_rubygems_version = Gem::Requirement.new(">= 2.6".freeze)
   s.require_paths = ["lib".freeze]