diff --git a/.github/workflows/crdroid-plus-kernel-build.yml b/.github/workflows/crdroid-plus-kernel-build.yml
index 45e2c09..98cc582 100644
--- a/.github/workflows/crdroid-plus-kernel-build.yml
+++ b/.github/workflows/crdroid-plus-kernel-build.yml
@@ -437,6 +437,18 @@ jobs:
             fi
           fi
 
+          # CRITICAL FIX v39: FINAL umount fix - runs AFTER pre-patched file
+          # The pre-patched file still contains umount() calls that don't exist in kernel 4.9
+          echo "=== CRITICAL FIX v39: FINAL aggressive umount -> sys_umount fix ==="
+
+          if [ -f "$GITHUB_WORKSPACE/build-scripts/fix_kernelsu_49_v39.py" ]; then
+            echo "Running kernel 4.9 compatibility fix script v39 (FINAL)..."
+            KERNEL_DIR=~/kernel-build/android_kernel_oneplus_sdm845 python3 "$GITHUB_WORKSPACE/build-scripts/fix_kernelsu_49_v39.py" ~/kernel-build/android_kernel_oneplus_sdm845
+          elif [ -f "$GITHUB_WORKSPACE/fix_kernelsu_49_v39.py" ]; then
+            echo "Running kernel 4.9 compatibility fix script v39 from repo root..."
+            KERNEL_DIR=~/kernel-build/android_kernel_oneplus_sdm845 python3 "$GITHUB_WORKSPACE/fix_kernelsu_49_v39.py" ~/kernel-build/android_kernel_oneplus_sdm845
+          fi
+
           # Verification: Show line 591 of core_hook.c to verify the fix
           echo "=== Verifying core_hook.c line 591 (flags fix) ==="
           CORE_HOOK_FILE=$(readlink -f drivers/kernelsu/core_hook.c 2>/dev/null || echo "")
diff --git a/build-scripts/__pycache__/fix_kernelsu_49_v39.cpython-311.pyc b/build-scripts/__pycache__/fix_kernelsu_49_v39.cpython-311.pyc
new file mode 100644
index 0000000..71900f4
Binary files /dev/null and b/build-scripts/__pycache__/fix_kernelsu_49_v39.cpython-311.pyc differ
diff --git a/build-scripts/fix_kernelsu_49_v39.py b/build-scripts/fix_kernelsu_49_v39.py
new file mode 100644
index 0000000..e79071f
--- /dev/null
+++ b/build-scripts/fix_kernelsu_49_v39.py
@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+"""
+KernelSU-Next kernel 4.9 compatibility fix script v39
+FINAL FIX: Aggressive umount() -> sys_umount() replacement for kernel 4.9
+
+Issue: The pre-patched core_hook.c.patched file contains umount() calls
+which don't exist in kernel 4.9. This fix runs AFTER the pre-patched file
+is applied to ensure all umount calls are replaced.
+
+This fix is designed to be the FINAL and MOST AGGRESSIVE fix.
+"""
+
+import sys
+import os
+import re
+
+def aggressive_umount_fix(file_path):
+    """Aggressively replace all umount() calls with sys_umount()"""
+
+    if not os.path.exists(file_path):
+        return False, "File not found"
+
+    with open(file_path, 'r') as f:
+        content = f.read()
+
+    original_content = content
+    changes = []
+
+    # Pattern 1: Direct umount(something) -> sys_umount(something, 0)
+    # This is the most common pattern causing the undefined reference
+    pattern1 = r'(?<!sys_)(?<!try_)\bumount\s*\(\s*([^,)]+)\s*\)'
+    matches1 = list(re.finditer(pattern1, content))
+    if matches1:
+        content = re.sub(pattern1, r'sys_umount(\1, 0)', content)
+        changes.append(f"Replaced {len(matches1)} umount(X) calls with sys_umount(X, 0)")
+
+    # Pattern 2: Handle any remaining umount with two args (shouldn't exist but be safe)
+    pattern2 = r'(?<!sys_)(?<!try_)\bumount\s*\('
+    matches2 = list(re.finditer(pattern2, content))
+    if matches2:
+        changes.append(f"WARNING: Found {len(matches2)} remaining umount calls that need manual fix")
+        for i, match in enumerate(matches2):
+            # Get surrounding context
+            start = max(0, match.start() - 20)
+            end = min(len(content), match.end() + 40)
+            context = content[start:end]
+            changes.append(f"  Match {i+1}: ...{context}...")
+
+    # Check if any changes were made
+    if content != original_content:
+        with open(file_path, 'w') as f:
+            f.write(content)
+        return True, changes
+    else:
+        return False, "No umount() calls found to fix"
+
+
+def ensure_sys_umount_declaration(file_path):
+    """Ensure sys_umount is declared for kernel 4.9"""
+
+    with open(file_path, 'r') as f:
+        content = f.read()
+
+    # Check if already declared
+    if 'asmlinkage long sys_umount' in content or 'extern long sys_umount' in content:
+        return False, "sys_umount already declared"
+
+    # Add declaration after includes
+    declaration = '''/* Kernel 4.9 compatibility */
+asmlinkage long sys_umount(const char __user *name, int flags);
+'''
+
+    # Find last #include line
+    lines = content.split('\n')
+    insert_idx = 0
+    for i, line in enumerate(lines):
+        if line.startswith('#include'):
+            insert_idx = i + 1
+
+    lines.insert(insert_idx, declaration)
+    content = '\n'.join(lines)
+
+    with open(file_path, 'w') as f:
+        f.write(content)
+
+    return True, "Added sys_umount declaration"
+
+
+def process_core_hook_files(kernel_dir):
+    """Process all possible core_hook.c locations with deduplication"""
+
+    possible_paths = [
+        os.path.join(kernel_dir, 'drivers/kernelsu/core_hook.c'),
+        os.path.join(kernel_dir, 'drivers/kernelsu/KernelSU/kernel/core_hook.c'),
+        os.path.join(kernel_dir, 'KernelSU/kernel/core_hook.c'),
+        os.path.join(kernel_dir, 'KernelSU-Next/kernel/core_hook.c'),
+    ]
+
+    results = []
+    seen_paths = set()  # Track processed real paths to avoid duplicates
+
+    for path in possible_paths:
+        if not os.path.exists(path):
+            continue
+
+        real_path = os.path.realpath(path)
+
+        # Skip if we've already processed this real file
+        if real_path in seen_paths:
+            continue
+        seen_paths.add(real_path)
+
+        print(f"\nProcessing: {real_path}")
+
+        # Apply aggressive umount fix
+        fixed, msg = aggressive_umount_fix(real_path)
+        if fixed:
+            print(f"  [FIXED] {msg}")
+        else:
+            print(f"  [INFO] {msg}")
+
+        # Ensure declaration exists
+        declared, msg = ensure_sys_umount_declaration(real_path)
+        if declared:
+            print(f"  [DECLARED] {msg}")
+
+        results.append((real_path, fixed, declared))
+
+    return results
+
+
+def main():
+    kernel_dir = os.environ.get('KERNEL_DIR', '')
+
+    if len(sys.argv) > 1:
+        kernel_dir = sys.argv[1]
+
+    if not kernel_dir:
+        print("Usage: KERNEL_DIR=/path/to/kernel python3 fix_kernelsu_49_v39.py [kernel_dir]")
+        sys.exit(1)
+
+    print("=" * 60)
+    print("KernelSU-Next 4.9 Compatibility Fix v39 (FINAL)")
+    print("=" * 60)
+    print(f"Kernel directory: {kernel_dir}")
+    print("")
+    print("This fix aggressively replaces ALL umount() calls with sys_umount()")
+    print("It runs AFTER the pre-patched file is applied.")
+    print("")
+
+    results = process_core_hook_files(kernel_dir)
+
+    print("\n" + "=" * 60)
+    print("SUMMARY")
+    print("=" * 60)
+
+    if results:
+        for path, fixed, _declared in results:
+            status = "FIXED" if fixed else "OK"
+            print(f"  [{status}] {path}")
+        print("\nv39 fix applied. Build should now succeed.")
+        return 0
+
+    print("  WARNING: No core_hook.c files found!")
+    print(f"  Searched in: {kernel_dir}")
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())