1 files changed, 1 insertions, 1 deletions
diff --git a/rts/Capability.c b/rts/Capability.c
index 181075b963..9a0c92174d 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -1256,7 +1256,7 @@ void
 setIOManagerControlFd(uint32_t cap_no USED_IF_THREADS, int fd USED_IF_THREADS) {
 #if defined(THREADED_RTS)
     if (cap_no < n_capabilities) {
-        capabilities[cap_no]->io_manager_control_wr_fd = fd;
+        RELAXED_STORE(&capabilities[cap_no]->io_manager_control_wr_fd, fd);
     } else {
         errorBelch("warning: setIOManagerControlFd called with illegal capability number.");
     }