diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 3c9544017..20720fb99 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -568,7 +568,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
                     /* On macOS, accepted sockets inherit the
                        non-blocking flag from the server socket, so
                        explicitly make it blocking. */
-                    if (fcntl(fdServer.get(), F_SETFL, fcntl(fdServer.get(), F_GETFL) & ~O_NONBLOCK) == -1)
+                    if (fcntl(fdClient.get(), F_SETFL, fcntl(fdClient.get(), F_GETFL) & ~O_NONBLOCK) == -1)
                         abort();
 
                     while (true) {