diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
index 9c29727337..0297871bdd 100644
--- a/hw/ppc/pnv.c
+++ b/hw/ppc/pnv.c
@@ -1623,7 +1623,8 @@ static void pnv_chip_power9_realize(DeviceState *dev, Error **errp)
             return;
         }
         pnv_xscom_add_subregion(chip, PNV9_XSCOM_I2CM_BASE +
-                               chip9->i2c[i].engine * PNV9_XSCOM_I2CM_SIZE,
+                                (chip9->i2c[i].engine - 1) *
+                                        PNV9_XSCOM_I2CM_SIZE,
                                 &chip9->i2c[i].xscom_regs);
         qdev_connect_gpio_out(DEVICE(&chip9->i2c[i]), 0,
                               qdev_get_gpio_in(DEVICE(&chip9->psi),
@@ -1871,7 +1872,8 @@ static void pnv_chip_power10_realize(DeviceState *dev, Error **errp)
             return;
         }
         pnv_xscom_add_subregion(chip, PNV10_XSCOM_I2CM_BASE +
-                                chip10->i2c[i].engine * PNV10_XSCOM_I2CM_SIZE,
+                                (chip10->i2c[i].engine - 1) *
+                                        PNV10_XSCOM_I2CM_SIZE,
                                 &chip10->i2c[i].xscom_regs);
         qdev_connect_gpio_out(DEVICE(&chip10->i2c[i]), 0,
                               qdev_get_gpio_in(DEVICE(&chip10->psi),
diff --git a/hw/ppc/pnv_i2c.c b/hw/ppc/pnv_i2c.c
index 483d91d15a..384442f898 100644
--- a/hw/ppc/pnv_i2c.c
+++ b/hw/ppc/pnv_i2c.c
@@ -594,7 +594,7 @@ static int pnv_i2c_dt_xscom(PnvXScomInterface *dev, void *fdt,
     int i2c_offset;
     const char i2c_compat[] = "ibm,power8-i2cm\0ibm,power9-i2cm";
     uint32_t i2c_pcba = PNV9_XSCOM_I2CM_BASE +
-        i2c->engine * PNV9_XSCOM_I2CM_SIZE;
+        (i2c->engine - 1) * PNV9_XSCOM_I2CM_SIZE;
     uint32_t reg[2] = {
         cpu_to_be32(i2c_pcba),
         cpu_to_be32(PNV9_XSCOM_I2CM_SIZE)