diff --git a/packages/ctl/src/commands.js b/packages/ctl/src/commands.js
index c5f3fe9d..a99e9eb7 100644
--- a/packages/ctl/src/commands.js
+++ b/packages/ctl/src/commands.js
@@ -867,6 +867,9 @@ modPackCommands.add(new libCommand.Command({
 		yargs.positional("mod-pack", { describe: "Mod pack to show", type: "string" });
 	}],
 	handler: async function(args, control) {
+		let mods = new Map(
+			(await libLink.messages.listMods.send(control)).list.map(m => [`${m.name}_${m.version}`, m])
+		);
 		let response = await libLink.messages.getModPack.send(control, {
 			id: await libCommand.resolveModPack(control, args.modPack),
 		});
@@ -875,8 +878,12 @@ modPackCommands.add(new libCommand.Command({
 			if (field === "mods") {
 				print(`${field}:`);
 				for (let entry of value) {
+					const mod = mods.get(`${entry.name}_${entry.version}`);
+					const missing = !mod && "? ";
+					const badChecksum = mod && entry.sha1 && entry.sha1 !== mod.sha1 && "! ";
+					const warn = missing || badChecksum || "";
 					const enabled = entry.enabled ? "" : "(disabled) ";
-					print(`  ${enabled}${entry.name} ${entry.version}${entry.sha1 ? ` (${entry.sha1})` : ""}`);
+					print(`  ${warn}${enabled}${entry.name} ${entry.version}${entry.sha1 ? ` (${entry.sha1})` : ""}`);
 				}
 			} else if (field === "settings") {
 				print(`${field}:`);
diff --git a/packages/web_ui/src/components/ModDetails.jsx b/packages/web_ui/src/components/ModDetails.jsx
index af5ebd78..19487421 100644
--- a/packages/web_ui/src/components/ModDetails.jsx
+++ b/packages/web_ui/src/components/ModDetails.jsx
@@ -1,5 +1,6 @@
 import React, { Fragment } from "react";
 import { Descriptions, Grid, Typography } from "antd";
+import ExclamationCircleOutlined from "@ant-design/icons/ExclamationCircleOutlined";
 
 import { libHelpers } from "@clusterio/lib";
 
@@ -11,6 +12,12 @@ export default function ModDetails(props) {
 	const mod = props.mod;
 
 	return <Descriptions className="borderless" bordered size="small" column={{ xs: 1, sm: 1, md: 1, lg: 2 }}>
+		{mod.error && <Descriptions.Item label={<><ExclamationCircleOutlined/> Error</>} span={2}>
+			{mod.error === "missing" && "The given version of this mod is missing from the master storage."}
+			{mod.error === "bad_checksum"
+				&& "Checksum of the mod in the master storage does not match the checksum provided by this mod pack."
+			}
+		</Descriptions.Item>}
 		{props.actions && !screens.lg
 			&& <Descriptions.Item label="Action">{props.actions(mod)}</Descriptions.Item>
 		}
diff --git a/packages/web_ui/src/components/ModPackViewPage.jsx b/packages/web_ui/src/components/ModPackViewPage.jsx
index 4507f534..0d2a426f 100644
--- a/packages/web_ui/src/components/ModPackViewPage.jsx
+++ b/packages/web_ui/src/components/ModPackViewPage.jsx
@@ -6,6 +6,8 @@ import {
 } from "antd";
 import InfoCircleOutlined from "@ant-design/icons/InfoCircleOutlined";
 import ExportOutlined from "@ant-design/icons/ExportOutlined";
+import FileUnknownOutlined from "@ant-design/icons/FileUnknownOutlined";
+import FileExclamationOutlined from "@ant-design/icons/FileExclamationOutlined";
 import CloseOutlined from "@ant-design/icons/CloseOutlined";
 import DeleteOutlined from "@ant-design/icons/DeleteOutlined";
 import PlusOutlined from "@ant-design/icons/PlusOutlined";
@@ -213,8 +215,16 @@ function ModsTable(props) {
 	const mods = [...props.modPack.mods.values(), ...deletedMods.values()].map(
 		mod => {
 			const candidate = modListMap.get(`${mod.name}_${mod.version}`);
-			if (!candidate || mod.sha1 && candidate.sha1 !== mod.sha1) {
-				return mod;
+			if (!candidate) {
+				return {
+					...mod,
+					error: "missing",
+				};
+			} else if (mod.sha1 && candidate.sha1 !== mod.sha1) {
+				return {
+					...mod,
+					error: "bad_checksum",
+				};
 			}
 			return candidate;
 		}
@@ -289,7 +299,15 @@ function ModsTable(props) {
 				{
 					title: "Name",
 					key: "name",
-					render: mod => mod.title || mod.name,
+					render: mod => <>
+						{mod.error === "missing" && <Tooltip title="Mod is missing from storage.">
+							<FileUnknownOutlined style={{ color: "#a61d24" }} />{" "}
+						</Tooltip>}
+						{mod.error === "bad_checksum" && <Tooltip title="Mod checksum missmatch.">
+							<FileExclamationOutlined style={{ color: "#a61d24" }} />{" "}
+						</Tooltip>}
+						{mod.title || mod.name}
+					</>,
 					defaultSortOrder: "ascend",
 					sorter: (a, b) => strcmp(a.name, b.name),
 				},