diff --git a/openflexure_microscope/exceptions.py b/openflexure_microscope/exceptions.py
index 250eae65..73db926f 100644
--- a/openflexure_microscope/exceptions.py
+++ b/openflexure_microscope/exceptions.py
@@ -1,2 +1,20 @@
+from threading import ThreadError
+
 class TaskDeniedException(Exception):
-    pass
\ No newline at end of file
+    pass
+
+class LockError(ThreadError):
+    ERROR_CODES = {
+        'ACQUIRE_ERROR': "Unable to acquire. Lock in use by another thread.",
+        'IN_USE_ERROR': "Lock in use by another thread."
+    }
+
+    def __init__(self, code, lock):
+        self.code = code
+        if code in LockError.ERROR_CODES:
+            self.message = LockError.ERROR_CODES[code]
+        else:
+            self.message = "Unknown error."
+        print("{}: {}".format(self.code, self.message))
+
+        ThreadError.__init__(self)
\ No newline at end of file