diff --git a/client.js b/client.js
index d0e6f96d..09c12488 100644
--- a/client.js
+++ b/client.js
@@ -157,7 +157,7 @@ class Instance extends link.Link{
 
 		// Find plugin modules to patch in
 		let modules = new Map();
-		for (let pluginName of this.plugins.keys()) {
+		for (let [pluginName, plugin] of this.plugins) {
 			let modulePath = path.join('plugins', pluginName, 'module');
 			if (!await fs.pathExists(modulePath)) {
 				continue;
@@ -174,12 +174,16 @@ class Instance extends link.Link{
 			}
 
 			module = Object.assign({
+				version: plugin.info.version,
+				dependencies: {},
 				path: modulePath,
 				load: [],
 			}, module);
 			modules.set(module.name, module);
 		}
 
+		// Find stand alone modules to load
+		// XXX for now it's assumed all available modules should be loaded.
 		for (let entry of await fs.readdir('modules', { withFileTypes: true })) {
 			if (entry.isDirectory()) {
 				if (modules.has(entry.name)) {
@@ -198,13 +202,14 @@ class Instance extends link.Link{
 
 				module = Object.assign({
 					path: path.join('modules', entry.name),
+					dependencies: {},
 					load: [],
 				}, module);
 				modules.set(module.name, module);
 			}
 		}
 
-		await factorio.patch(this.path("saves", saveName), modules.values());
+		await factorio.patch(this.path("saves", saveName), [...modules.values()]);
 
 		this.server.on('rcon-ready', () => {
 			console.log("Clusterio | RCON connection established");
diff --git a/docs/developing-for-clusterio.md b/docs/developing-for-clusterio.md
index 6083285e..41e9ac5f 100644
--- a/docs/developing-for-clusterio.md
+++ b/docs/developing-for-clusterio.md
@@ -198,6 +198,10 @@ structure:
 ```json
 {
     "name": "my_module",
+    "version": "1.2.0",
+    "dependencies": {
+        "foo": ">=0.4.2"
+    },
     "load": ["foo.lua"]
 }
 ```
@@ -208,6 +212,19 @@ The following entries are supported in the module.json file:
     Name of the module, must match the folder the module is located in
     for stand alone modules or the name of the plugin the module is
     located in.
+- `version`:
+    Version of the module.  Must be compatible with [Semantic Versioning
+    2.0.0](https://semver.org/).  In plugin modules this defaults to the
+    version of the plugin otherwise it's required.
+- `dependencies`:
+    Optional mapping of modules this module depends on and their
+    version.  In the example `>=0.4.2` means that the foo module must be
+    at least version 0.4.2.  See the [Ranges
+    syntax](https://www.npmjs.com/package/semver#ranges) of the
+    node-semver package for a full description of what operators are
+    supported.  The events for dependencies is invoked before the events
+    of the dependent, and starting an instance will fail if the
+    dependencies cannot be satisfied.
 - `load`:
     Lua files to load with the `event_handler` lib.  They should be
     specified as paths that's relative to the module and uses forward
diff --git a/docs/writing-plugins.md b/docs/writing-plugins.md
index 9926e845..9a0f65af 100644
--- a/docs/writing-plugins.md
+++ b/docs/writing-plugins.md
@@ -52,7 +52,9 @@ The following properties are recognized:
     Brief description of what the plugin does.  Currently not used.
 
 **version**:
-    Semver compatible version string of the plugin.  Currently not used.
+    Semver compatible version string of the plugin.  Currently only
+    servers as the default for the Clusterio module embedded in the
+    plugin, if any.
 
 **instanceEntrypoint**:
     Path to a Node.js module relative to the plugin directory which
diff --git a/lib/factorio/patch.js b/lib/factorio/patch.js
index 41ebf1c0..93c51bc0 100644
--- a/lib/factorio/patch.js
+++ b/lib/factorio/patch.js
@@ -8,6 +8,7 @@ const events = require("events");
 const fs = require("fs-extra");
 const jszip = require("jszip");
 const path = require("path");
+const semver = require("semver");
 
 const hash = require("lib/hash");
 
@@ -94,6 +95,99 @@ function generateLoader(patchInfo) {
 	return lines.join('\n');
 }
 
+/**
+ * Reorders modules to satisfy their dependencies
+ *
+ * Looks through and reorders the array of module definitions in order to
+ * satisfy the property that dependencies are earlier in the array than
+ * their dependents.  Throws an error if this is not possible.
+ *
+ * @param {Array<Object>} modules - Array of modules to reorder
+ */
+function reorderDependencies(modules) {
+	let index = 0;
+	let present = new Map();
+	let hold = new Map();
+	reorder: while (index < modules.length) {
+		let module = modules[index];
+		if (semver.valid(module.version) === null) {
+			throw new Error(`Invalid version '${module.version}' for module ${module.name}`);
+		}
+
+		for (let [dependency, requirement] of Object.entries(module.dependencies)) {
+			if (semver.validRange(requirement) === null) {
+				throw new Error(
+					`Invalid version range '${requirement}' for dependency ${dependency} on module ${module.name}`
+				);
+			}
+
+			if (present.has(dependency)) {
+				if (!semver.satisfies(present.get(dependency), requirement)) {
+					throw new Error(`Module ${module.name} requires ${dependency} ${requirement}`);
+				}
+
+			// We have an unmet dependency, take it out and continue
+			} else {
+				if (hold.has(dependency)) {
+					hold.get(dependency).push(module);
+				} else {
+					hold.set(dependency, [module]);
+				}
+				modules.splice(index, 1);
+				continue reorder;
+			}
+		}
+
+		// No unmet dependencies, record and continue
+		present.set(module.name, module.version);
+		index++;
+
+		if (hold.has(module.name)) {
+			modules.splice(index, 0, ...hold.get(module.name));
+			hold.delete(module.name);
+		}
+	}
+
+	if (!hold.size) {
+		return;
+	}
+
+	// There are three reasons for a module to end up being held: The module depends
+	// on a module that is missing, the module is part of a dependency loop, or the
+	// the module depends on a module that satisfy any of these conditions.
+
+	let remaining = new Map();
+	for (let modules of hold.values()) {
+		for (let module of modules) {
+			remaining.set(module.name, module);
+		}
+	}
+
+	// Start with a random module from the remaining modules
+	for (let module of remaining.values()) {
+		let cycle = [];
+		while (true) {
+			// Find an unmet dependency
+			let dependency = Object.keys(module.dependencies).find(name => !present.has(name));
+
+			if (!remaining.has(dependency)) {
+				// There's no module being held up by this dependency, the
+				// dependency is missing.
+				throw new Error(`Missing dependency ${dependency} for module ${module.name}`);
+			}
+
+			if (cycle.includes(module.name)) {
+				cycle.push(module.name);
+				cycle.splice(0, cycle.indexOf(module.name))
+				throw new Error(`Module dependency loop detected: ${cycle.join(" -> ")}`);
+			}
+
+			cycle.push(module.name);
+			module = remaining.get(dependency);
+		}
+	}
+}
+
 /**
  * Patch a save with the given modules
  *
@@ -135,6 +229,8 @@ async function patch(savePath, modules) {
 		zip.remove(file.name);
 	}
 
+	reorderDependencies(modules);
+
 	// Add the modules to the save.
 	for (let module of modules) {
 		let moduleDir = root.folder(`modules/${module.name}`);
@@ -182,4 +278,5 @@ module.exports = {
 	// For testing only
 	_findRoot: findRoot,
 	_generateLoader: generateLoader,
+	_reorderDependencies: reorderDependencies,
 }
diff --git a/package.json b/package.json
index 2ea38232..e596efdf 100644
--- a/package.json
+++ b/package.json
@@ -56,6 +56,7 @@
     "rcon-client": "^4.2.0",
     "request": "^2.83.0",
     "sanitizer": "^0.1.3",
+    "semver": "^7.1.1",
     "set-blocking": "^2.0.0",
     "simple-git": "^1.96.0",
     "single-line-log": "^1.1.2",
diff --git a/test/integration/patch.js b/test/integration/patch.js
index 9897bc28..8fc96c23 100644
--- a/test/integration/patch.js
+++ b/test/integration/patch.js
@@ -23,10 +23,14 @@ describe("Integration of lib/factorio/patch", function() {
 			slowTest(this);
 			await factorio.patch(savePath, [{
 				name: "test",
+				version: "1.0.0",
+				dependencies: {},
 				path: "test/file/modules/test",
 				load: [],
 			}, {
 				name: "subdir",
+				version: "1.0.0",
+				dependencies: {},
 				path: "test/file/modules/subdir",
 				load: [],
 			}]);
diff --git a/test/lib/factorio/patch.js b/test/lib/factorio/patch.js
index 3815a852..75f07553 100644
--- a/test/lib/factorio/patch.js
+++ b/test/lib/factorio/patch.js
@@ -78,6 +78,132 @@ describe("lib/factorio", function() {
 		});
 	});
 
+	describe("reorderDependencies()", function() {
+		it("should reorder to satisfy simple dependency", function() {
+			let modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {'b': '*'} },
+				{ name: 'b', version: '1.0.0', dependencies: {} },
+			];
+			factorio._reorderDependencies(modules);
+			assert(modules[0].name === 'b', "Dependency was not reorederd");
+		});
+		it("should throw on invalid version", function() {
+			let modules = [
+				{ name: 'a', version: 'foo', dependencies: {} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Invalid version 'foo' for module a")
+			);
+		});
+		it("should throw on invalid version range", function() {
+			let modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {'b': 'invalid'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Invalid version range 'invalid' for dependency b on module a")
+			);
+		});
+		it("should throw on missing dependency", function() {
+			let modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {'b': '*'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Missing dependency b for module a")
+			);
+			modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {'b': '*'} },
+				{ name: 'b', version: '1.0.0', dependencies: {'c': '*'} },
+				{ name: 'c', version: '1.0.0', dependencies: {'d': '*'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Missing dependency d for module c")
+			);
+		});
+		it("should throw on outdated dependency", function() {
+			let modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {} },
+				{ name: 'b', version: '1.0.0', dependencies: {'a': '>=2'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Module b requires a >=2")
+			);
+		});
+		it("should throw on dependency loops", function() {
+			let modules = [
+				{ name: 'a', version: '1.0.0', dependencies: {'b': '*'} },
+				{ name: 'b', version: '1.0.0', dependencies: {'a': '*'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Module dependency loop detected: a -> b -> a")
+			);
+			modules = [
+				{ name: 'd', version: '1.0.0', dependencies: {'b': '*'} },
+				{ name: 'a', version: '1.0.0', dependencies: {'b': '*'} },
+				{ name: 'b', version: '1.0.0', dependencies: {'c': '*'} },
+				{ name: 'c', version: '1.0.0', dependencies: {'a': '*'} },
+			];
+			assert.throws(
+				() => factorio._reorderDependencies(modules),
+				new Error("Module dependency loop detected: b -> c -> a -> b")
+			);
+		});
+		it("should reorder correctly for multiple dependencies", function() {
+			function validate(modules) {
+				let present = new Set();
+				for (let module of modules) {
+					for (let dependency of Object.keys(module.dependencies)) {
+						if (!present.has(dependency)) {
+							assert.fail(`${module.name} depends on ${dependency}, but was ordered before it`);
+						}
+					}
+					present.add(module.name);
+				}
+			}
+
+			let names = ['a', 'b', 'c'];
+			let successCount = 0;
+			const bitCount = names.length * (names.length - 1);
+			for (let i=0; i < 2**bitCount; i++) {
+				let value = i;
+				let bits = [];
+				for (let j=0; j < bitCount; j++) {
+					bits.push(value & 1);
+					value >>= 1;
+				}
+				let modules = [];
+				for (let j=0; j < names.length; j++) {
+					let name = names[j];
+					let dependencies = {};
+					for (let k=0; k < names.length - 1; k++) {
+						if (bits[k + j * (names.length - 1)]) {
+							dependencies[names[k + (k >= j)]] = '*';
+						}
+					}
+					modules.push({ name, version: '1.0.0', dependencies });
+				}
+				let success = false;
+				try {
+					factorio._reorderDependencies(modules);
+					success = true;
+				} catch (err) { }
+				if (success) {
+					validate(modules);
+					successCount++;
+				}
+			}
+
+			// Deriving the formula for the number of graphs without
+			// dependencies loops is left as an excercise for the reader.
+			assert(successCount === 25, "Incorrect number of successful orderings");
+		});
+	});
+
 	describe("patch()", function() {
 		it("should throw on unknown scenario", async function() {
 			let zip = new jszip();