diff --git a/src/globals.c b/src/globals.c
index 393a4e2..536d67e 100644
--- a/src/globals.c
+++ b/src/globals.c
@@ -16,7 +16,7 @@
 
 #include "globals.h"
 
-int_fast8_t C_SIMPLE_HTTP_KEEP_RUNNING = 1;
-int_fast8_t C_SIMPLE_HTTP_SIGUSR1_SET = 0;
+volatile int_fast8_t C_SIMPLE_HTTP_KEEP_RUNNING = 1;
+volatile int_fast8_t C_SIMPLE_HTTP_SIGUSR1_SET = 0;
 
 // vim: et ts=2 sts=2 sw=2
diff --git a/src/globals.h b/src/globals.h
index cd8e5d9..70886d6 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -20,8 +20,8 @@
 // Standard library includes.
 #include <stdint.h>
 
-extern int_fast8_t C_SIMPLE_HTTP_KEEP_RUNNING;
-extern int_fast8_t C_SIMPLE_HTTP_SIGUSR1_SET;
+extern volatile int_fast8_t C_SIMPLE_HTTP_KEEP_RUNNING;
+extern volatile int_fast8_t C_SIMPLE_HTTP_SIGUSR1_SET;
 
 #endif