diff --git a/lib/Resource.js b/lib/Resource.js
index 860b68e6..3d38fd55 100644
--- a/lib/Resource.js
+++ b/lib/Resource.js
@@ -70,11 +70,14 @@ class Resource {
 			birthtime: new Date()
 		};
 
-		this._createStream = createStream || null;
-		this._stream = stream || null;
-		this._buffer = buffer || null;
-		if (typeof string === "string" || string instanceof String) {
-			this._buffer = Buffer.from(string, "utf8");
+		if (createStream) {
+			this._createStream = createStream;
+		} else if (stream) {
+			this._stream = stream;
+		} else if (buffer) {
+			this.setBuffer(buffer);
+		} else if (typeof string === "string" || string instanceof String) {
+			this.setString(string);
 		}
 
 		// Tracing:
@@ -117,6 +120,7 @@ class Resource {
 		this._buffer = buffer;
 		this._contentDrained = false;
 		this._streamDrained = false;
+		this._setSize(this._buffer.byteLength);
 	}
 
 	/**
@@ -207,6 +211,17 @@ class Resource {
 		this._streamDrained = false;
 	}
 
+	/**
+	 * Set the size in bytes
+	 *
+	 * @param {number} size byte size
+	 * @private
+	 * @see https://nodejs.org/api/fs.html#fs_stats_size
+	 */
+	_setSize(size) {
+		this._statInfo.size = size;
+	}
+
 	/**
 	 * Gets the resources path
 	 *
diff --git a/test/lib/Resource.js b/test/lib/Resource.js
index c2400601..fef77d1e 100644
--- a/test/lib/Resource.js
+++ b/test/lib/Resource.js
@@ -2,6 +2,8 @@ const test = require("ava");
 const Stream = require("stream");
 const fs = require("fs");
 const path = require("path");
+const {promisify} = require("util");
+const stat = promisify(fs.stat);
 const Resource = require("../../lib/Resource");
 
 function createBasicResource() {
@@ -142,6 +144,58 @@ test("Resource: setString", (t) => {
 	});
 });
 
+test("Resource: size modification", async (t) => {
+	const resource = new Resource({
+		path: "my/path/to/resource"
+	});
+	t.falsy(resource.getStatInfo().size, "initial size is not defined");
+
+	// string
+	resource.setString("Content");
+
+	t.is(resource.getStatInfo().size, 7, "size after manually setting the string");
+	t.is(new Resource({
+		path: "my/path/to/resource",
+		string: "Content"
+	}).getStatInfo().size, 7, "size when passing string to constructor");
+
+
+	// buffer
+	resource.setBuffer(Buffer.from("Super"));
+
+	t.is(resource.getStatInfo().size, 5, "size after manually setting the string");
+
+	const clonedResource1 = await resource.clone();
+	t.is(clonedResource1.getStatInfo().size, 5, "size after cloning the resource");
+
+
+	// buffer with alloc
+	const buf = Buffer.alloc(1234);
+	buf.write("some string", 0, "utf8");
+	resource.setBuffer(buf);
+
+	t.is(resource.getStatInfo().size, 1234, "buffer with alloc after setting the buffer");
+	t.is(new Resource({
+		path: "my/path/to/resource",
+		buffer: buf
+	}).getStatInfo().size, 1234, "buffer with alloc when passing buffer to constructor");
+
+	const clonedResource2 = await resource.clone();
+	t.is(clonedResource2.getStatInfo().size, 1234, "buffer with alloc atfer clone");
+});
+
+test("Resource: _setSize", (t) => {
+	t.plan(1);
+
+	const resource = new Resource({
+		path: "my/path/to/resource"
+	});
+
+	resource._setSize(1337);
+
+	t.is(resource.getStatInfo().size, 1337);
+});
+
 test("Resource: setStream", (t) => {
 	t.plan(1);
 
@@ -267,3 +321,24 @@ test("getBuffer from Stream content: Subsequent content requests should not thro
 	// to throw "Content stream of Resource /app/index.html is flagged as drained."
 	await t.notThrowsAsync(p2);
 });
+
+test("integration stat - resource size", async (t) => {
+	const fsPath = path.join("test", "fixtures", "application.a", "webapp", "index.html");
+	const statInfo = await stat(fsPath);
+
+	const resource = new Resource({
+		path: fsPath,
+		statInfo,
+		createStream: () => {
+			return fs.createReadStream(fsPath);
+		}
+	});
+	t.is(resource.getStatInfo().size, 91);
+
+	// Setting the same content again should end up with the same size
+	resource.setString(await resource.getString());
+	t.is(resource.getStatInfo().size, 91);
+
+	resource.setString("myvalue");
+	t.is(resource.getStatInfo().size, 7);
+});