diff --git a/hw/xfree86/os-support/bus/nobus.c b/hw/xfree86/os-support/bus/nobus.c
index dca58fee2..dc36ecd0a 100644
--- a/hw/xfree86/os-support/bus/nobus.c
+++ b/hw/xfree86/os-support/bus/nobus.c
@@ -1,5 +1,5 @@
 static void
-__noop_to_appease_ar__()
+__noop_to_appease_ar__(void)
 {
     return;
 }
diff --git a/hw/xfree86/os-support/shared/agp_noop.c b/hw/xfree86/os-support/shared/agp_noop.c
index 9c6ed4b8d..da486c051 100644
--- a/hw/xfree86/os-support/shared/agp_noop.c
+++ b/hw/xfree86/os-support/shared/agp_noop.c
@@ -47,7 +47,7 @@ xf86GARTCloseScreen(int screenNum)
 }
 
 Bool
-xf86AgpGARTSupported()
+xf86AgpGARTSupported(void)
 {
     return FALSE;
 }
diff --git a/hw/xfree86/os-support/shared/ioperm_noop.c b/hw/xfree86/os-support/shared/ioperm_noop.c
index 30688c0b5..eeacee9cc 100644
--- a/hw/xfree86/os-support/shared/ioperm_noop.c
+++ b/hw/xfree86/os-support/shared/ioperm_noop.c
@@ -36,13 +36,13 @@
 #include "xf86_OSlib.h"
 
 Bool
-xf86EnableIO()
+xf86EnableIO(void)
 {
     return TRUE;
 }
 
 void
-xf86DisableIO()
+xf86DisableIO(void)
 {
     return;
 }
diff --git a/hw/xfree86/os-support/stub/stub_init.c b/hw/xfree86/os-support/stub/stub_init.c
index 629675d68..d3e0c3f29 100644
--- a/hw/xfree86/os-support/stub/stub_init.c
+++ b/hw/xfree86/os-support/stub/stub_init.c
@@ -5,12 +5,12 @@
 #include "xf86_OSlib.h"
 
 void
-xf86OpenConsole()
+xf86OpenConsole(void)
 {
 }
 
 void
-xf86CloseConsole()
+xf86CloseConsole(void)
 {
 }
 
@@ -21,6 +21,6 @@ xf86ProcessArgument(int argc, char *argv[], int i)
 }
 
 void
-xf86UseMsg()
+xf86UseMsg(void)
 {
 }