--- a/sys/dev/drm/amd/display/dc/irq_types.h
+++ b/sys/dev/drm/amd/display/dc/irq_types.h
@@ -154,8 +154,8 @@ enum irq_type
 	IRQ_TYPE_VBLANK = DC_IRQ_SOURCE_VBLANK1,
 };
 
 #define DAL_VALID_IRQ_SRC_NUM(src) \
-	((src) <= DAL_IRQ_SOURCES_NUMBER && (src) > DC_IRQ_SOURCE_INVALID)
+	((src) < DAL_IRQ_SOURCES_NUMBER && (src) > DC_IRQ_SOURCE_INVALID)
 
 /* Number of Page Flip IRQ Sources. */
 #define DAL_PFLIP_IRQ_SRC_NUM \
 	(DC_IRQ_SOURCE_PFLIP_LAST - DC_IRQ_SOURCE_PFLIP_FIRST + 1)