diff --git a/ChangeLog.md b/ChangeLog.md
index 104d5f017105e..ead54a346cbae 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -22,6 +22,11 @@ See docs/process.md for more on how version tagging works.
 -----------------------
 - `-z` arguments are now passed directly to wasm-ld without the need for the
   `-Wl,` prefix.  This matches the behaviour of both clang and gcc. (#18956)
+- Reverted #18525 which runs the JS pre-processor over files passed via
+  --pre-js and --post-js.  It turned out this change caused issue for several
+  folks who had JS files with lines that start with `#` so can't be run through
+  the pre-processor.  If folks want to re-enable this we can looks into ways to
+  make it conditional/optional.
 
 3.1.34 - 03/14/23
 -----------------
diff --git a/src/jsifier.js b/src/jsifier.js
index 01faabd03da42..804355b3e8ec3 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -457,6 +457,12 @@ function ${name}(${args}) {
     print(`// end include: ${fileName}`);
   }
 
+  function includeFileRaw(fileName) {
+    print(`// include: ${fileName}`);
+    print(read(fileName));
+    print(`// end include: ${fileName}`);
+  }
+
   function finalCombiner() {
     const splitPostSets = splitter(postSets, (x) => x.symbol && x.dependencies);
     postSets = splitPostSets.leftIn;
@@ -525,7 +531,7 @@ function ${name}(${args}) {
     includeFile(postFile);
 
     for (const fileName of POST_JS_FILES) {
-      includeFile(fileName);
+      includeFileRaw(fileName);
     }
 
     print('//FORWARDED_DATA:' + JSON.stringify({
diff --git a/src/parseTools.js b/src/parseTools.js
index 49d569ad55290..be894884d048f 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -991,7 +991,7 @@ function getEntryFunction() {
 function preJS() {
   let result = '';
   for (const fileName of PRE_JS_FILES) {
-    result += preprocess(fileName);
+    result += read(fileName);
   }
   return result;
 }
diff --git a/test/test_other.py b/test/test_other.py
index 9b5376b8485c5..a41b1cfa83e71 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -9295,21 +9295,6 @@ def test_js_preprocess(self):
     self.assertContained('JSLIB: EXIT_RUNTIME', err)
     self.assertNotContained('JSLIB: MAIN_MODULE', err)
 
-  def test_js_preprocess_pre_post(self):
-    create_file('pre.js', '''
-    #if ASSERTIONS
-    console.log('assertions enabled')
-    #else
-    console.log('assertions disabled')
-    #endif
-    ''')
-    create_file('post.js', '''
-    console.log({{{ POINTER_SIZE }}});
-    ''')
-    self.emcc_args += ['--pre-js', 'pre.js', '--post-js', 'post.js']
-    self.do_runf(test_file('hello_world.c'), 'assertions enabled\n4')
-    self.do_runf(test_file('hello_world.c'), 'assertions disabled\n4', emcc_args=['-sASSERTIONS=0'])
-
   def test_html_preprocess(self):
     src_file = test_file('module/test_stdin.c')
     output_file = 'test_stdin.html'