diff --git a/src/main/java/com/dostalgia/UploadResource.java b/src/main/java/com/dostalgia/UploadResource.java
index 1e5c8c9..b1d569b 100644
--- a/src/main/java/com/dostalgia/UploadResource.java
+++ b/src/main/java/com/dostalgia/UploadResource.java
@@ -293,15 +293,16 @@ public class UploadResource {
             Files.walk(extractDir).filter(Files::isRegularFile).forEach(f -> {
                 try {
                     String entryName = extractDir.relativize(f).toString().replace('\\', '/');
-                    // Ensure all parent directories have explicit entries
-                    // (js-dos Emscripten FS requires explicit directory entries)
+                    // Ensure ALL ancestor directories have explicit entries
+                    // (Emscripten FS requires every directory in the chain)
                     int idx = entryName.lastIndexOf('/');
-                    if (idx >= 0) {
+                    while (idx >= 0) {
                         String parent = entryName.substring(0, idx + 1);
                         if (addedDirs.add(parent)) {
                             zos.putNextEntry(new java.util.zip.ZipEntry(parent));
                             zos.closeEntry();
                         }
+                        idx = entryName.lastIndexOf('/', idx - 1);
                     }
                     zos.putNextEntry(new java.util.zip.ZipEntry(entryName));
                     Files.copy(f, zos);