diff --git a/hw/xfree86/os-support/bsd/bsd_init.c b/hw/xfree86/os-support/bsd/bsd_init.c
index 2cd2b57c7c..6fdf6d4e68 100644
--- a/hw/xfree86/os-support/bsd/bsd_init.c
+++ b/hw/xfree86/os-support/bsd/bsd_init.c
@@ -663,7 +663,7 @@ xf86UseMsg()
 }
 
 void
-xf86OSInputThreadInit()
+xf86OSInputThreadInit(void)
 {
     return;
 }
diff --git a/hw/xfree86/os-support/hurd/hurd_init.c b/hw/xfree86/os-support/hurd/hurd_init.c
index ee8fe92c07..c1b632f19b 100644
--- a/hw/xfree86/os-support/hurd/hurd_init.c
+++ b/hw/xfree86/os-support/hurd/hurd_init.c
@@ -89,7 +89,7 @@ xf86CloseConsole()
 }
 
 void
-xf86OSInputThreadInit()
+xf86OSInputThreadInit(void)
 {
     return;
 }
diff --git a/hw/xfree86/os-support/linux/lnx_init.c b/hw/xfree86/os-support/linux/lnx_init.c
index 9ef6a39b5b..111b3b4e41 100644
--- a/hw/xfree86/os-support/linux/lnx_init.c
+++ b/hw/xfree86/os-support/linux/lnx_init.c
@@ -409,7 +409,7 @@ xf86UseMsg(void)
 }
 
 void
-xf86OSInputThreadInit()
+xf86OSInputThreadInit(void)
 {
     return;
 }
diff --git a/hw/xfree86/os-support/solaris/sun_vid.c b/hw/xfree86/os-support/solaris/sun_vid.c
index edb0a1172f..2b48e66b0f 100644
--- a/hw/xfree86/os-support/solaris/sun_vid.c
+++ b/hw/xfree86/os-support/solaris/sun_vid.c
@@ -74,7 +74,7 @@ xf86OSInitVidMem(VidMemInfoPtr pVidMem)
 /***************************************************************************/
 
 void
-xf86OSInputThreadInit()
+xf86OSInputThreadInit(void)
 {
     /*
      * Need to enable in input thread as well, as Solaris kernel tracks
diff --git a/hw/xfree86/os-support/stub/stub_init.c b/hw/xfree86/os-support/stub/stub_init.c
index 1285ec4821..f0d9039b9b 100644
--- a/hw/xfree86/os-support/stub/stub_init.c
+++ b/hw/xfree86/os-support/stub/stub_init.c
@@ -26,7 +26,7 @@ xf86UseMsg(void)
 }
 
 void
-xf86OSInputThreadInit()
+xf86OSInputThreadInit(void)
 {
     return;
 }