diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index a1b7512d46..ef1d7d48d2 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -485,7 +485,7 @@ static STORAGE_BUS_TYPE win2qemu[] = {
 
 static GuestDiskBusType find_bus_type(STORAGE_BUS_TYPE bus)
 {
-    if (bus > ARRAY_SIZE(win2qemu) || (int)bus < 0) {
+    if (bus >= ARRAY_SIZE(win2qemu) || (int)bus < 0) {
         return GUEST_DISK_BUS_TYPE_UNKNOWN;
     }
     return win2qemu[(int)bus];