diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
index f903f265f9f..3a664523c27 100644
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -1154,6 +1154,9 @@ acpi_child_deleted(device_t dev, device_t child)
     free(dinfo, M_ACPIDEV);
 }
 
+_Static_assert(ACPI_IVAR_PRIVATE >= ISA_IVAR_LAST,
+    "ACPI private IVARs overlap with ISA IVARs");
+
 /*
  * Handle per-device ivars
  */
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
index d1d55d2b7e5..336f6ed1dc9 100644
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -278,10 +278,10 @@ extern int	acpi_override_isa_irq_polarity;
  * attach to ACPI.
  */
 enum {
-	ACPI_IVAR_HANDLE = BUS_IVARS_ACPI,
-	ACPI_IVAR_PRIVATE,
+	ACPI_IVAR_PRIVATE = 20,
 	ACPI_IVAR_FLAGS,
-	ACPI_IVAR_DOMAIN
+	ACPI_IVAR_DOMAIN,
+	ACPI_IVAR_HANDLE = BUS_IVARS_ACPI
 };
 
 /*
diff --git a/sys/isa/isavar.h b/sys/isa/isavar.h
index f0b880de293..39eb7c2bc76 100644
--- a/sys/isa/isavar.h
+++ b/sys/isa/isavar.h
@@ -128,7 +128,8 @@ enum isa_device_ivars {
 	ISA_IVAR_CONFIGATTR,
 	ISA_IVAR_PNP_CSN,
 	ISA_IVAR_PNP_LDN,
-	ISA_IVAR_PNPBIOS_HANDLE
+	ISA_IVAR_PNPBIOS_HANDLE,
+	ISA_IVAR_LAST
 };
 
 /*