diff --git a/CHANGES.md b/CHANGES.md
index 1a26791..0ff9db2 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,6 +1,8 @@
 # Changelog
 
 ## Unreleased
+- Build Script: Replace version instead of appending to the index file.
+
 
 ## 2024/05/21 v0.0.2
 - Initial release
diff --git a/cratedb_sqlparse_js/cratedb_sqlparse/index.js b/cratedb_sqlparse_js/cratedb_sqlparse/index.js
index 344bb4a..692a1f4 100644
--- a/cratedb_sqlparse_js/cratedb_sqlparse/index.js
+++ b/cratedb_sqlparse_js/cratedb_sqlparse/index.js
@@ -1,2 +1,3 @@
 import {sqlparse} from "./parser.js";
 export {sqlparse};
+export const __cratedb_version__ = "5.6.4"
diff --git a/cratedb_sqlparse_py/cratedb_sqlparse/__init__.py b/cratedb_sqlparse_py/cratedb_sqlparse/__init__.py
index c9b943b..6146498 100644
--- a/cratedb_sqlparse_py/cratedb_sqlparse/__init__.py
+++ b/cratedb_sqlparse_py/cratedb_sqlparse/__init__.py
@@ -1,3 +1,5 @@
 from .parser import ParsingException, sqlparse
 
 __all__ = ["sqlparse", "ParsingException"]
+
+__cratedb_version__ = "5.6.4"
diff --git a/setup_grammar.py b/setup_grammar.py
index c834f8c..3ed23eb 100644
--- a/setup_grammar.py
+++ b/setup_grammar.py
@@ -2,6 +2,7 @@
 import logging
 import subprocess
 import sys
+import re
 from enum import Enum
 from pathlib import Path
 
@@ -137,9 +138,18 @@ def set_version(target: Antlr4Target, version: str):
         index_file = 'index.js'
         variable = 'export const __cratedb_version__'
 
-    # FIXME: Need to apply "replace" instead of "append"?
-    with open(target_path / index_file, "a") as f:
-        f.write(f"{variable} = {version}\n")
+    with open(target_path / index_file, "r+") as f:
+        content = f.read()
+
+        # Removes the current content on disk.
+        f.seek(0)
+        f.truncate()
+
+        updated_content = re.sub(f'({variable} = )"(.*)"', r'\1' + version, content)
+
+        f.write(updated_content)
+
+    logger.info(f'Updated  {variable} to {version} in {index_file}')
 
 
 if __name__ == '__main__':
@@ -150,14 +160,17 @@ def set_version(target: Antlr4Target, version: str):
     TODO: Improve efficiency by generating runtime parser for all implemented languages at once.
     """
     setup_logging()
+
     input_target = sys.argv[1]
     version = '5.6.4'
+
     if input_target.startswith("py"):
         target = Antlr4Target.python
     elif input_target.startswith("js") or input_target.startswith("java"):
         target = Antlr4Target.js
     else:
         raise NotImplementedError(f"Parser generator for target {input_target} not implemented")
+
     download_cratedb_grammar(version)
     compile_grammar(target)
     patch_lexer(target)