diff --git a/src/libutil/include/nix/util/lru-cache.hh b/src/libutil/include/nix/util/lru-cache.hh
index 686b73149..c9bcd7ee0 100644
--- a/src/libutil/include/nix/util/lru-cache.hh
+++ b/src/libutil/include/nix/util/lru-cache.hh
@@ -105,12 +105,12 @@ public:
         return value;
     }
 
-    size_t size() const
+    size_t size() const noexcept
     {
         return data.size();
     }
 
-    void clear()
+    void clear() noexcept
     {
         data.clear();
         lru.clear();