diff --git a/hw/xfree86/common/xf86Bus.h b/hw/xfree86/common/xf86Bus.h
index 07ba4b1f1..4c0bc19ab 100644
--- a/hw/xfree86/common/xf86Bus.h
+++ b/hw/xfree86/common/xf86Bus.h
@@ -75,7 +75,10 @@ extern int pciSlotClaimed;
 Bool xf86ComparePciBusString(const char *busID, int bus, int device, int func);
 Bool xf86DriverHasEntities(DriverPtr drvp);
 void xf86RemoveEntityFromScreen(ScrnInfoPtr pScrn, int entityIndex);
+
+_X_EXPORT /* only for internal int10 module - not supposed to be used by OOT drivers */
 Bool xf86IsEntityPrimary(int entityIndex);
+
 ScrnInfoPtr xf86FindScreenForEntity(int entityIndex);
 
 Bool xf86BusConfig(void);