diff --git a/disked/disked.c b/disked/disked.c
index 92a548a8..929b7401 100644
--- a/disked/disked.c
+++ b/disked/disked.c
@@ -886,7 +886,7 @@ static void unscan_partition(struct partition* p)
 	bdev->fs_error = FILESYSTEM_ERROR_NONE;
 }
 
-static void unscan_device()
+static void unscan_device(void)
 {
 	if ( !current_hd )
 		return;
@@ -922,7 +922,7 @@ static void scan_partition(struct partition* p)
 		                      filesystem_error_string(bdev->fs_error));
 }
 
-static void scan_device()
+static void scan_device(void)
 {
 	if ( !current_hd )
 		return;
diff --git a/init/init.c++ b/init/init.c++
index a4857897..eeaf8c53 100644
--- a/init/init.c++
+++ b/init/init.c++
@@ -227,7 +227,7 @@ static bool prepare_block_device(void* ctx, const char* path)
 	return true;
 }
 
-static void prepare_block_devices()
+static void prepare_block_devices(void)
 {
 	static bool done = false;
 	if ( done )
@@ -367,7 +367,7 @@ static void load_fstab(void)
 	      sort_mountpoint);
 }
 
-static void set_hostname()
+static void set_hostname(void)
 {
 	FILE* fp = fopen("/etc/hostname", "r");
 	if ( !fp && errno == ENOENT )
@@ -384,7 +384,7 @@ static void set_hostname()
 		return warning("unable to set hostname: `%s': %m", hostname);
 }
 
-static void set_kblayout()
+static void set_kblayout(void)
 {
 	FILE* fp = fopen("/etc/kblayout", "r");
 	if ( !fp && errno == ENOENT )
@@ -409,7 +409,7 @@ static void set_kblayout()
 	free(kblayout);
 }
 
-static void set_videomode()
+static void set_videomode(void)
 {
 	FILE* fp = fopen("/etc/videomode", "r");
 	if ( !fp && errno == ENOENT )
@@ -455,7 +455,7 @@ static void set_videomode()
 		        xres, yres, bpp);
 }
 
-static void init_early()
+static void init_early(void)
 {
 	static bool done = false;
 	if ( done )
diff --git a/sysinstall/sysinstall.c b/sysinstall/sysinstall.c
index d213a415..1da54aaf 100644
--- a/sysinstall/sysinstall.c
+++ b/sysinstall/sysinstall.c
@@ -239,7 +239,7 @@ static char etc[] = "/tmp/etc.XXXXXX";
 static bool fs_made = false;
 static char fs[] = "/tmp/fs.XXXXXX";
 
-static void unmount_all_but_root()
+static void unmount_all_but_root(void)
 {
 	for ( size_t n = mountpoints_used; n != 0; n-- )
 	{