diff --git a/programs/msiexec/service.c b/programs/msiexec/service.c
index da552a712e6..3ccdb5bb58b 100644
--- a/programs/msiexec/service.c
+++ b/programs/msiexec/service.c
@@ -32,7 +32,7 @@ static SERVICE_STATUS_HANDLE hstatus;
 static HANDLE thread;
 static HANDLE kill_event;
 
-void KillService(void)
+static void KillService(void)
 {
     WINE_TRACE("Killing service\n");
     SetEvent(kill_event);