diff --git a/include/drm/i915_drm.h b/include/drm/i915_drm.h
index b1755f8..4e1b274 100644
--- a/include/drm/i915_drm.h
+++ b/include/drm/i915_drm.h
@@ -93,6 +93,6 @@
 #define    I845_TSEG_SIZE_1M	(3 << 1)
 
 #define INTEL_BSM 0x5c
-#define   INTEL_BSM_MASK (0xFFFF << 20)
+#define   INTEL_BSM_MASK	(-(1u << 20))
 
 #endif				/* _I915_DRM_H_ */