diff --git a/drivers/mbmmodem/gprs-context.c b/drivers/mbmmodem/gprs-context.c
index 0a1ca2c3..b9b4574e 100644
--- a/drivers/mbmmodem/gprs-context.c
+++ b/drivers/mbmmodem/gprs-context.c
@@ -514,12 +514,12 @@ static struct ofono_gprs_context_driver driver = {
 	.deactivate_primary	= mbm_gprs_deactivate_primary,
 };
 
-void mbm_gprs_context_init()
+void mbm_gprs_context_init(void)
 {
 	ofono_gprs_context_driver_register(&driver);
 }
 
-void mbm_gprs_context_exit()
+void mbm_gprs_context_exit(void)
 {
 	ofono_gprs_context_driver_unregister(&driver);
 }
diff --git a/drivers/mbmmodem/mbmmodem.h b/drivers/mbmmodem/mbmmodem.h
index 65786d7f..4c6f2633 100644
--- a/drivers/mbmmodem/mbmmodem.h
+++ b/drivers/mbmmodem/mbmmodem.h
@@ -21,8 +21,8 @@
 
 #include <drivers/atmodem/atutil.h>
 
-extern void mbm_gprs_context_init();
-extern void mbm_gprs_context_exit();
+extern void mbm_gprs_context_init(void);
+extern void mbm_gprs_context_exit(void);
 
-extern void mbm_stk_init();
-extern void mbm_stk_exit();
+extern void mbm_stk_init(void);
+extern void mbm_stk_exit(void);
diff --git a/drivers/mbmmodem/stk.c b/drivers/mbmmodem/stk.c
index 81c36dba..d0a9f3b2 100644
--- a/drivers/mbmmodem/stk.c
+++ b/drivers/mbmmodem/stk.c
@@ -270,12 +270,12 @@ static struct ofono_stk_driver driver = {
 	.terminal_response	= mbm_stk_terminal_response,
 };
 
-void mbm_stk_init()
+void mbm_stk_init(void)
 {
 	ofono_stk_driver_register(&driver);
 }
 
-void mbm_stk_exit()
+void mbm_stk_exit(void)
 {
 	ofono_stk_driver_unregister(&driver);
 }