diff --git a/ekernel.py b/ekernel.py
index 50cd736..d8a720a 100644
--- a/ekernel.py
+++ b/ekernel.py
@@ -173,11 +173,12 @@ def efi (f):
                     if f"already mounted on {Kernel.esp}" not in msg:
                         raise RuntimeError(e.stderr.decode().splitlines()[0])
             assert Kernel.boot.exists()
-        r = f(*args, **kwargs)
-        # umount esp
-        if mounted:
-            subprocess.run(["umount", str(Kernel.esp)], check=True)
-        return r
+        try:
+            return f(*args, **kwargs)
+        finally:
+            # umount esp
+            if mounted:
+                subprocess.run(["umount", str(Kernel.esp)], check=True)
     return locator
 
 @cli
diff --git a/tests/test_clean.py b/tests/test_clean.py
index 6448949..134cc68 100644
--- a/tests/test_clean.py
+++ b/tests/test_clean.py
@@ -100,6 +100,15 @@ class Tests (unittest.TestCase):
         self.assertEqual(run("-q", "-k", "10"), 0)
         self.check_clean(10)
 
+    @capture_stdout
+    def test_clean_umount_on_error (self):
+        with self.assertRaises(SystemExit):
+            self.assertEqual(run("-h"), 0)
+        tracer, (args, kwargs) = self.interceptor.trace[-1]
+        self.assertEqual(tracer.name, "subprocess.run")
+        self.assertEqual(args, (["umount", "/tmp"],))
+        self.assertEqual(kwargs, {"check": True})
+
     @colorless
     @capture_stdout
     def test_clean_dry_run (self):
diff --git a/tests/test_install.py b/tests/test_install.py
index 9a62ac1..763efeb 100644
--- a/tests/test_install.py
+++ b/tests/test_install.py
@@ -82,3 +82,7 @@ class Tests (unittest.TestCase):
         with self.assertRaises(SystemExit):
             self.assertEqual(run("-s", str(data.latest)), 1)
         self.assertRegex(sys.stderr.getvalue(), r"missing.*bzImage")
+        tracer, (args, kwargs) = self.interceptor.trace[-1]
+        self.assertEqual(tracer.name, "subprocess.run")
+        self.assertEqual(args, (["umount", "/tmp"],))
+        self.assertEqual(kwargs, {"check": True})