diff --git a/scripts/build/chroot_firmware b/scripts/build/chroot_firmware
index 4a65d552a..7fdd7605d 100755
--- a/scripts/build/chroot_firmware
+++ b/scripts/build/chroot_firmware
@@ -79,9 +79,25 @@ Firmware_List_From_Contents "${LB_PARENT_MIRROR_CHROOT}" "${LB_PARENT_DISTRIBUTI
 
 if [ "${LB_DERIVATIVE}" = "true" ]
 then
-	# FIXME: account for the fact that PARENT_DISTRIBUTION and DISTRIBUTION might be the same (to not have overlapping cache files for contents).
+	# Avoid downloading things twice if distributions are identical
+	DERIVATIVE_ARCHIVE_AREAS=""
+	if [ "${LB_DISTRIBUTION_CHROOT}" != "${LB_PARENT_DISTRIBUTION_CHROOT}" ]
+	then
+		DERIVATIVE_ARCHIVE_AREAS="${LB_ARCHIVE_AREAS}"
+	else
+		for _ARCHIVE_AREA in ${LB_ARCHIVE_AREAS}
+		do
+			if ! In_list ${_ARCHIVE_AREA} "${LB_PARENT_ARCHIVE_AREAS}"
+			then
+				DERIVATIVE_ARCHIVE_AREAS="${DERIVATIVE_ARCHIVE_AREAS} ${_ARCHIVE_AREA}"
+			fi
+		done
+	fi
 
-	Firmware_List_From_Contents "${LB_MIRROR_CHROOT}" "${LB_DISTRIBUTION_CHROOT}" "${LB_ARCHIVE_AREAS}"
+	if [ ! -z "${DERIVATIVE_ARCHIVE_AREAS}" ]
+	then
+		Firmware_List_From_Contents "${LB_MIRROR_CHROOT}" "${LB_DISTRIBUTION_CHROOT}" "${DERIVATIVE_ARCHIVE_AREAS}"
+	fi
 fi
 
 # Drop section and keep package names only
diff --git a/scripts/build/installer_debian-installer b/scripts/build/installer_debian-installer
index 67573f2e6..64375e85c 100755
--- a/scripts/build/installer_debian-installer
+++ b/scripts/build/installer_debian-installer
@@ -367,9 +367,25 @@ then
 
 		if [ "${LB_DERIVATIVE}" = "true" ]
 		then
-			# FIXME: account for the fact that PARENT_DISTRIBUTION and DISTRIBUTION might be the same (to not have overlapping cache files for contents).
+			# Avoid downloading things twice if distributions are identical
+			DERIVATIVE_ARCHIVE_AREAS=""
+			if [ "${LB_DISTRIBUTION_CHROOT}" != "${LB_PARENT_DISTRIBUTION_CHROOT}" ]
+			then
+				DERIVATIVE_ARCHIVE_AREAS="${LB_ARCHIVE_AREAS}"
+			else
+				for _ARCHIVE_AREA in ${LB_ARCHIVE_AREAS}
+				do
+					if ! In_list ${_ARCHIVE_AREA} "${LB_PARENT_ARCHIVE_AREAS}"
+					then
+						DERIVATIVE_ARCHIVE_AREAS="${DERIVATIVE_ARCHIVE_AREAS} ${DERIVATIVE_ARCHIVE_AREAS}"
+					fi
+				done
+			fi
 
-			Firmware_List_From_Contents "${LB_MIRROR_CHROOT}" "${LB_DISTRIBUTION_CHROOT}" "${LB_ARCHIVE_AREAS}"
+			if [ ! -z "${DERIVATIVE_ARCHIVE_AREAS}" ]
+			then
+				Firmware_List_From_Contents "${LB_MIRROR_CHROOT}" "${LB_DISTRIBUTION_CHROOT}" "${DERIVATIVE_ARCHIVE_AREAS}"
+			fi
 		fi
 
 		# Drop section and keep package names only