diff --git a/packages/@stylexjs/stylex/package.json b/packages/@stylexjs/stylex/package.json
index e019ef591..ab95b4763 100644
--- a/packages/@stylexjs/stylex/package.json
+++ b/packages/@stylexjs/stylex/package.json
@@ -65,5 +65,6 @@
   },
   "files": [
     "lib/*"
-  ]
+  ],
+  "sideEffects": false
 }
diff --git a/packages/@stylexjs/stylex/rollup.config.mjs b/packages/@stylexjs/stylex/rollup.config.mjs
index 1de6c89b6..91c18f3ce 100644
--- a/packages/@stylexjs/stylex/rollup.config.mjs
+++ b/packages/@stylexjs/stylex/rollup.config.mjs
@@ -31,6 +31,24 @@ const config = {
       babelHelpers: 'bundled',
       configFile: path.resolve(__dirname, '.babelrc.js'),
     }),
+    {
+      name: 'legacy-merge-export-pure',
+      transform(code, id) {
+        if (id === path.resolve(__dirname, 'src/stylex.js')) {
+          const newCode = code.replace(
+            'export const legacyMerge =',
+            'export const legacyMerge = /*@__PURE__*/',
+          );
+          if (newCode === code) {
+            throw new Error(
+              'Expect to find to "export const legacyMerge =" in src/stylex.js',
+            );
+          }
+          return newCode;
+        }
+        return code;
+      },
+    },
     resolve(),
     commonjs(),
   ],
diff --git a/packages/@stylexjs/stylex/src/stylex.js b/packages/@stylexjs/stylex/src/stylex.js
index ff5185734..a6d9d318a 100644
--- a/packages/@stylexjs/stylex/src/stylex.js
+++ b/packages/@stylexjs/stylex/src/stylex.js
@@ -262,25 +262,26 @@ type IStyleX = {
   ...
 };
 
-function _legacyMerge(
-  ...styles: $ReadOnlyArray<StyleXArray<?CompiledStyles | boolean>>
-): string {
-  const [className] = styleq(styles);
-  return className;
-}
-
-_legacyMerge.create = create;
-_legacyMerge.createTheme = createTheme;
-_legacyMerge.defineConsts = defineConsts;
-_legacyMerge.defineMarker = defineMarker;
-_legacyMerge.defineVars = defineVars;
-_legacyMerge.defaultMarker = defaultMarker;
-_legacyMerge.firstThatWorks = firstThatWorks;
-_legacyMerge.keyframes = keyframes;
-_legacyMerge.positionTry = positionTry;
-_legacyMerge.props = props;
-_legacyMerge.types = types;
-_legacyMerge.when = when;
-_legacyMerge.viewTransitionClass = viewTransitionClass;
+export const legacyMerge: IStyleX = /*@__PURE__*/ (function () {
+  function _legacyMerge(
+    ...styles: $ReadOnlyArray<StyleXArray<?CompiledStyles | boolean>>
+  ): string {
+    const [className] = styleq(styles);
+    return className;
+  }
 
-export const legacyMerge: IStyleX = _legacyMerge;
+  _legacyMerge.create = create;
+  _legacyMerge.createTheme = createTheme;
+  _legacyMerge.defineConsts = defineConsts;
+  _legacyMerge.defineMarker = defineMarker;
+  _legacyMerge.defineVars = defineVars;
+  _legacyMerge.defaultMarker = defaultMarker;
+  _legacyMerge.firstThatWorks = firstThatWorks;
+  _legacyMerge.keyframes = keyframes;
+  _legacyMerge.positionTry = positionTry;
+  _legacyMerge.props = props;
+  _legacyMerge.types = types;
+  _legacyMerge.when = when;
+  _legacyMerge.viewTransitionClass = viewTransitionClass;
+  return _legacyMerge;
+})();