diff --git a/darwin-user/signal.c b/darwin-user/signal.c
index 8dbfa931e1..aeb8a622ad 100644
--- a/darwin-user/signal.c
+++ b/darwin-user/signal.c
@@ -54,7 +54,7 @@ struct emulated_sigaction {
                              first signal, we put it here */
 };
 
-struct sigaltstack target_sigaltstack_used = {
+static struct sigaltstack target_sigaltstack_used = {
     0, 0, SA_DISABLE
 };
 
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 96409233c8..88f6a21785 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -31,7 +31,7 @@
 
 //#define DEBUG_SIGNAL
 
-struct target_sigaltstack target_sigaltstack_used = {
+static struct target_sigaltstack target_sigaltstack_used = {
     .ss_sp = 0,
     .ss_size = 0,
     .ss_flags = TARGET_SS_DISABLE,