diff --git a/src/thread/Thread.hxx b/src/thread/Thread.hxx
index c0d35a91c..3a92db5a0 100644
--- a/src/thread/Thread.hxx
+++ b/src/thread/Thread.hxx
@@ -57,6 +57,7 @@ public:
 	explicit Thread(Function _f) noexcept:f(_f) {}
 
 	Thread(const Thread &) = delete;
+	Thread &operator=(const Thread &) = delete;
 
 #ifndef NDEBUG
 	~Thread() noexcept {