diff --git a/osbuild/__init__.py b/osbuild/__init__.py
index e68dad4f..1e0f8bbb 100644
--- a/osbuild/__init__.py
+++ b/osbuild/__init__.py
@@ -44,31 +44,30 @@ class AssemblerFailed(Exception):
 
 class TmpFs:
     def __init__(self, path="/run/osbuild"):
-        self.root = tempfile.mkdtemp(prefix="osbuild-tmpfs-", dir=path)
+        self.path = path
+        self.root = None
         self.mounted = False
+
+    def __enter__(self):
+        self.root = tempfile.mkdtemp(prefix="osbuild-tmpfs-", dir=self.path)
         try:
             subprocess.run(["mount", "-t", "tmpfs", "-o", "mode=0755", "tmpfs", self.root], check=True)
             self.mounted = True
         except subprocess.CalledProcessError:
-            self.unmount()
+            os.rmdir(self.root)
+            self.root = None
+            raise
+        return self.root
 
-    def unmount(self):
+    def __exit__(self, exc_type, exc_value, exc_tb):
         if not self.root:
             return
         if self.mounted:
             subprocess.run(["umount", "--lazy", self.root], check=True)
+            self.mounted = False
         os.rmdir(self.root)
         self.root = None
 
-    def __del__(self):
-        self.unmount()
-
-    def __enter__(self):
-        return self.root
-
-    def __exit__(self, exc_type, exc_value, exc_tb):
-        self.unmount()
-
 
 class BuildRoot:
     def __init__(self, path="/run/osbuild"):