diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index e5a25d97f8db..992bc72cab6f 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2531,7 +2531,7 @@ static int allocate_vpe_l1_table(void)
 		npg = 1;
 	}
 
-	val |= FIELD_PREP(GICR_VPROPBASER_4_1_SIZE, npg);
+	val |= FIELD_PREP(GICR_VPROPBASER_4_1_SIZE, npg - 1);
 
 	/* Right, that's the number of CPU pages we need for L1 */
 	np = DIV_ROUND_UP(npg * psz, PAGE_SIZE);