diff --git a/ext/java/org/jruby/ext/stringio/StringIO.java b/ext/java/org/jruby/ext/stringio/StringIO.java
index 1628645..076b663 100644
--- a/ext/java/org/jruby/ext/stringio/StringIO.java
+++ b/ext/java/org/jruby/ext/stringio/StringIO.java
@@ -75,6 +75,9 @@ static class StringIOData {
     }
     StringIOData ptr;
 
+    private static final String
+    STRINGIO_VERSION = "3.0.9";
+
     private static final int STRIO_READABLE = ObjectFlags.registry.newFlag(StringIO.class);
     private static final int STRIO_WRITABLE = ObjectFlags.registry.newFlag(StringIO.class);
     private static final int STRIO_READWRITE = (STRIO_READABLE | STRIO_WRITABLE);
@@ -83,7 +86,7 @@ public static RubyClass createStringIOClass(final Ruby runtime) {
         RubyClass stringIOClass = runtime.defineClass(
                 "StringIO", runtime.getObject(), StringIO::new);
 
-        RubyString version = RubyString.newString(runtime, "3.0.9");
+        RubyString version = RubyString.newString(runtime, STRINGIO_VERSION);
         stringIOClass.defineConstant("VERSION", version);
 
         stringIOClass.defineAnnotatedMethods(StringIO.class);
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index d5753a9..43ce0d6 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -12,7 +12,8 @@
 
 **********************************************************************/
 
-#define STRINGIO_VERSION "3.0.9"
+static const char *const
+STRINGIO_VERSION = "3.0.9";
 
 #include "ruby.h"
 #include "ruby/io.h"
diff --git a/rakelib/version.rake b/rakelib/version.rake
index b2e4b61..97b18bd 100644
--- a/rakelib/version.rake
+++ b/rakelib/version.rake
@@ -2,13 +2,13 @@ class << (helper = Bundler::GemHelper.instance)
   C_SOURCE_PATH = "ext/stringio/stringio.c"
   JAVA_SOURCE_PATH = "ext/java/org/jruby/ext/stringio/StringIO.java"
   def update_source_version
-    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)
+    v = version.to_s
+    [C_SOURCE_PATH, JAVA_SOURCE_PATH].each do |path|
+      source = File.read(path)
+      if source.sub!(/^\s*STRINGIO_VERSION\s*=\s*"\K.*(?=")/) {break if $& == v; v}
+        File.write(path, source)
+      end
+    end
   end
 
   def commit_bump
diff --git a/stringio.gemspec b/stringio.gemspec
index c73fc3a..8c950f8 100644
--- a/stringio.gemspec
+++ b/stringio.gemspec
@@ -4,7 +4,7 @@
 source_version = ["", "ext/stringio/"].find do |dir|
   begin
     break File.open(File.join(__dir__, "#{dir}stringio.c")) {|f|
-      f.gets("\n#define STRINGIO_VERSION ")
+      f.gets("\nSTRINGIO_VERSION ")
       f.gets[/\s*"(.+)"/, 1]
     }
   rescue Errno::ENOENT