diff --git a/modules/abstract-utxo/package.json b/modules/abstract-utxo/package.json
index 503ba1e9be..69d7322ea0 100644
--- a/modules/abstract-utxo/package.json
+++ b/modules/abstract-utxo/package.json
@@ -25,7 +25,7 @@
   "scripts": {
     "build": "npm run build:cjs && npm run build:esm",
     "build:cjs": "yarn tsc --build --incremental --verbose .",
-    "build:esm": "yarn tsc --project tsconfig.esm.json",
+    "build:esm": "yarn tsc --project tsconfig.esm.json && node ../../scripts/fix-esm.js dist/esm",
     "fmt": "prettier --write '{src,test}/**/*.{ts,js,json}'",
     "check-fmt": "prettier --check '{src,test}/**/*.{ts,js,json}'",
     "clean": "rm -rf ./dist",
diff --git a/modules/utxo-core/package.json b/modules/utxo-core/package.json
index c766d91698..18229cb083 100644
--- a/modules/utxo-core/package.json
+++ b/modules/utxo-core/package.json
@@ -47,7 +47,7 @@
   "scripts": {
     "build": "npm run build:cjs && npm run build:esm",
     "build:cjs": "yarn tsc --build --incremental --verbose .",
-    "build:esm": "yarn tsc --project tsconfig.esm.json",
+    "build:esm": "yarn tsc --project tsconfig.esm.json && node ../../scripts/fix-esm.js dist/esm",
     "fmt": "prettier --write .",
     "check-fmt": "prettier --check '**/*.{ts,js,json}'",
     "clean": "rm -r ./dist",
diff --git a/scripts/fix-esm.js b/scripts/fix-esm.js
new file mode 100644
index 0000000000..f638262110
--- /dev/null
+++ b/scripts/fix-esm.js
@@ -0,0 +1,53 @@
+const fs = require('fs');
+const path = require('path');
+
+function processDir(dir) {
+  if (!fs.existsSync(dir)) return;
+  const files = fs.readdirSync(dir);
+  for (const file of files) {
+    const fullPath = path.join(dir, file);
+    if (fs.statSync(fullPath).isDirectory()) {
+      processDir(fullPath);
+    } else if (fullPath.endsWith('.js') || fullPath.endsWith('.d.ts')) {
+      let content = fs.readFileSync(fullPath, 'utf8');
+      // Regex to match import/export statements (including dynamic imports)
+      const regex = /(from\s+['"]|import\s*\(?['"]|import\s+['"])([^'"]+)(['"]\)?)/g;
+      
+      let modifiedContent = content.replace(regex, (match, p1, p2, p3) => {
+        // Skip if already has an extension or is a known standard module/bare module that doesn't need it
+        if (p2.endsWith('.js') || p2.endsWith('.json') || p2.endsWith('.cjs') || p2.endsWith('.mjs')) {
+          return match;
+        }
+
+        // Handle relative paths
+        if (p2.startsWith('.')) {
+          // If the path corresponds to a directory, it needs /index.js
+          const targetPath = path.join(path.dirname(fullPath), p2);
+          if (fs.existsSync(targetPath) && fs.statSync(targetPath).isDirectory()) {
+            return `${p1}${p2}/index.js${p3}`;
+          } else {
+            return `${p1}${p2}.js${p3}`;
+          }
+        }
+        
+        // Handle specific subpath third-party imports mentioned in the bug report
+        if (p2.startsWith('bip174/src/')) {
+          return `${p1}${p2}.js${p3}`;
+        }
+        
+        return match;
+      });
+
+      if (modifiedContent !== content) {
+        fs.writeFileSync(fullPath, modifiedContent, 'utf8');
+      }
+    }
+  }
+}
+
+const targetDir = process.argv[2];
+if (!targetDir) {
+  console.error("Usage: node fix-esm.js <directory>");
+  process.exit(1);
+}
+processDir(targetDir);