diff --git a/xarray/backends/locks.py b/xarray/backends/locks.py
index 784443544ee..16331b9d1b1 100644
--- a/xarray/backends/locks.py
+++ b/xarray/backends/locks.py
@@ -218,6 +218,9 @@ def __init__(self, locks: Sequence[Lock]):
         self.locks = tuple(set(locks))  # remove duplicates
 
     def acquire(self, blocking=True):
+        assert blocking, (
+            "Without blocking you will never know which locks you have to unlock!"
+        )
         return all(acquire(lock, blocking=blocking) for lock in self.locks)
 
     def release(self):