diff --git a/release/tools/ec2.conf b/release/tools/ec2.conf
--- a/release/tools/ec2.conf
+++ b/release/tools/ec2.conf
@@ -75,8 +75,9 @@
 	# (in fact the PL061 has no pullup/pulldown resistors).  Graviton 1
 	# through Graviton 3 have non-functional PCI _EJ0 and need a value
 	# written to the PCI power status register in order to eject a
-	# device.
-	echo 'debug.acpi.quirks="24"' >> ${DESTDIR}/boot/loader.conf
+	# device.  EC2 instances with PCI (not PCIe) buses need a short
+	# delay before rescanning upon device detach.
+	echo 'debug.acpi.quirks="56"' >> ${DESTDIR}/boot/loader.conf
 
 	# Load the kernel module for the Amazon "Elastic Network Adapter"
 	echo 'if_ena_load="YES"' >> ${DESTDIR}/boot/loader.conf
diff --git a/sys/dev/acpica/acpi_pci.c b/sys/dev/acpica/acpi_pci.c
--- a/sys/dev/acpica/acpi_pci.c
+++ b/sys/dev/acpica/acpi_pci.c
@@ -432,6 +432,8 @@
 			    acpi_name(h), AcpiFormatException(status));
 			return;
 		}
+		if (acpi_quirks & ACPI_Q_DELAY_BEFORE_EJECT_RESCAN)
+			DELAY(10 * 1000);
 		BUS_RESCAN(dev);
 		bus_topo_unlock();
 		break;
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -232,6 +232,8 @@
  *	as "PullUp" and they should be treated as "NoPull" instead.
  * ACPI_Q_CLEAR_PME_ON_DETACH: Specifies that PCIM_PSTAT_(PME & ~PMEENABLE)
  *	should be written to the power status register as part of ACPI Eject.
+ * ACPI_Q_DELAY_BEFORE_EJECT_RESCAN: Specifies that we need a short (10ms)
+ *	delay after _EJ0 returns before rescanning the PCI bus.
  */
 extern int	acpi_quirks;
 #define ACPI_Q_OK		0
@@ -240,6 +242,7 @@
 #define ACPI_Q_MADT_IRQ0	(1 << 2)
 #define ACPI_Q_AEI_NOPULL	(1 << 3)
 #define ACPI_Q_CLEAR_PME_ON_DETACH	(1 << 4)
+#define ACPI_Q_DELAY_BEFORE_EJECT_RESCAN	(1 << 5)
 
 #if defined(__amd64__) || defined(__i386__)
 /*