src/jdk.jextract/share/classes/com/sun/tools/jextract/Writer.java

@@ -39,11 +39,11 @@
     Writer(Context ctx, Map<String, byte[]> results) {
         this.log = ctx.log;
         this.results = results;
     }
 
-    static final String JEXTRACT_MANIFEST = "META-INF" + File.separatorChar + "jextract.properties";
+    static final String JEXTRACT_MANIFEST = "META-INF/jextract.properties";
 
     public boolean isEmpty() {
         return results.isEmpty();
     }
 

@@ -74,11 +74,11 @@
                 } catch (IOException ioe) {
                     throw new UncheckedIOException(ioe);
                 }
             });
 
-            Path propsPath = destDir.resolve(JEXTRACT_MANIFEST).normalize();
+            Path propsPath = destDir.resolve(JEXTRACT_MANIFEST.replace('/', File.separatorChar)).normalize();
             Files.createDirectories(propsPath.getParent());
             try (OutputStream fos = Files.newOutputStream(propsPath)) {
                 fos.write(getJextractProperties(args));
                 fos.flush();
             }