diff --git a/src/ast/nodes/AssignmentExpression.ts b/src/ast/nodes/AssignmentExpression.ts
index 98a539d3db5..9daabe0bd36 100644
--- a/src/ast/nodes/AssignmentExpression.ts
+++ b/src/ast/nodes/AssignmentExpression.ts
@@ -1,5 +1,5 @@
 import MagicString from 'magic-string';
-import { RenderOptions } from '../../utils/renderHelpers';
+import { findFirstOccurrenceOutsideComment, RenderOptions } from '../../utils/renderHelpers';
 import { getSystemExportStatement } from '../../utils/systemJsRendering';
 import { HasEffectsContext } from '../ExecutionContext';
 import { EMPTY_PATH, ObjectPath, UNKNOWN_PATH } from '../utils/PathTracker';
@@ -51,9 +51,19 @@ export default class AssignmentExpression extends NodeBase {
 		this.right.render(code, options);
 		if (options.format === 'system') {
 			if (this.left.variable && this.left.variable.exportName) {
-				code.prependLeft(
-					code.original.indexOf('=', this.left.end) + 1,
-					` exports('${this.left.variable.exportName}',`
+				const operatorPos = findFirstOccurrenceOutsideComment(
+					code.original,
+					this.operator,
+					this.left.end
+				);
+				const operation =
+					this.operator.length > 1
+						? ` ${this.left.variable.exportName} ${this.operator.slice(0, -1)}`
+						: '';
+				code.overwrite(
+					operatorPos,
+					operatorPos + this.operator.length,
+					`= exports('${this.left.variable.exportName}',${operation}`
 				);
 				code.appendLeft(this.right.end, `)`);
 			} else if ('addExportedVariables' in this.left) {
diff --git a/src/utils/renderHelpers.ts b/src/utils/renderHelpers.ts
index 92b9fdfc82f..3e4610ca9b6 100644
--- a/src/utils/renderHelpers.ts
+++ b/src/utils/renderHelpers.ts
@@ -30,7 +30,7 @@ export function findFirstOccurrenceOutsideComment(code: string, searchString: st
 	searchPos = code.indexOf(searchString, start);
 	while (true) {
 		start = code.indexOf('/', start);
-		if (start === -1 || start > searchPos) return searchPos;
+		if (start === -1 || start >= searchPos) return searchPos;
 		charCodeAfterSlash = code.charCodeAt(++start);
 		++start;
 
@@ -116,13 +116,13 @@ export function getCommaSeparatedNodesWithBoundaries<N extends Node>(
 	code: MagicString,
 	start: number,
 	end: number
-): ({
+): {
 	contentEnd: number;
 	end: number;
 	node: N;
 	separator: number | null;
 	start: number;
-})[] {
+}[] {
 	const splitUpNodes = [];
 	let node, nextNode, nextNodeStart, contentEnd, char;
 	let separator = start - 1;
diff --git a/test/form/samples/export-live-bindings/_expected/system.js b/test/form/samples/export-live-bindings/_expected/system.js
index 8d0ae5eca0e..9ed7fb7d347 100644
--- a/test/form/samples/export-live-bindings/_expected/system.js
+++ b/test/form/samples/export-live-bindings/_expected/system.js
@@ -10,7 +10,7 @@ System.register('iife', [], function (exports) {
       });
 
       function update () {
-        foo += exports('foo', 10);
+        foo = exports('foo', foo + 10);
       }
 
       let foo = exports('foo', 10);
diff --git a/test/form/samples/updating-assignments/_config.js b/test/form/samples/updating-assignments/_config.js
new file mode 100644
index 00000000000..b6633185ee0
--- /dev/null
+++ b/test/form/samples/updating-assignments/_config.js
@@ -0,0 +1,4 @@
+module.exports = {
+	description: 'Correctly handles assignment operators on exports',
+	options: { output: { name: 'bundle' } }
+};
diff --git a/test/form/samples/updating-assignments/_expected/amd.js b/test/form/samples/updating-assignments/_expected/amd.js
new file mode 100644
index 00000000000..addd8e09cdf
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/amd.js
@@ -0,0 +1,20 @@
+define(['exports'], function (exports) { 'use strict';
+
+	exports.x = 1;
+	exports.x = 2;
+	exports.x += 1;
+	exports.x -= 1;
+	exports.x *= 2;
+	exports.x /= 2;
+	exports.x %= 2;
+	exports.x **= 2;
+	exports.x <<= 1;
+	exports.x >>= 1;
+	exports.x >>>= 1;
+	exports.x &= 3;
+	exports.x ^= 2;
+	exports.x |= 2;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+});
diff --git a/test/form/samples/updating-assignments/_expected/cjs.js b/test/form/samples/updating-assignments/_expected/cjs.js
new file mode 100644
index 00000000000..3824b02062a
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/cjs.js
@@ -0,0 +1,18 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+exports.x = 1;
+exports.x = 2;
+exports.x += 1;
+exports.x -= 1;
+exports.x *= 2;
+exports.x /= 2;
+exports.x %= 2;
+exports.x **= 2;
+exports.x <<= 1;
+exports.x >>= 1;
+exports.x >>>= 1;
+exports.x &= 3;
+exports.x ^= 2;
+exports.x |= 2;
diff --git a/test/form/samples/updating-assignments/_expected/es.js b/test/form/samples/updating-assignments/_expected/es.js
new file mode 100644
index 00000000000..79bccd4fc74
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/es.js
@@ -0,0 +1,16 @@
+let x = 1;
+x = 2;
+x += 1;
+x -= 1;
+x *= 2;
+x /= 2;
+x %= 2;
+x **= 2;
+x <<= 1;
+x >>= 1;
+x >>>= 1;
+x &= 3;
+x ^= 2;
+x |= 2;
+
+export { x };
diff --git a/test/form/samples/updating-assignments/_expected/iife.js b/test/form/samples/updating-assignments/_expected/iife.js
new file mode 100644
index 00000000000..381fa322c49
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/iife.js
@@ -0,0 +1,21 @@
+var bundle = (function (exports) {
+	'use strict';
+
+	exports.x = 1;
+	exports.x = 2;
+	exports.x += 1;
+	exports.x -= 1;
+	exports.x *= 2;
+	exports.x /= 2;
+	exports.x %= 2;
+	exports.x **= 2;
+	exports.x <<= 1;
+	exports.x >>= 1;
+	exports.x >>>= 1;
+	exports.x &= 3;
+	exports.x ^= 2;
+	exports.x |= 2;
+
+	return exports;
+
+}({}));
diff --git a/test/form/samples/updating-assignments/_expected/system.js b/test/form/samples/updating-assignments/_expected/system.js
new file mode 100644
index 00000000000..78a7127d368
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/system.js
@@ -0,0 +1,23 @@
+System.register('bundle', [], function (exports) {
+	'use strict';
+	return {
+		execute: function () {
+
+			let x = exports('x', 1);
+			x = exports('x', 2);
+			x = exports('x', x + 1);
+			x = exports('x', x - 1);
+			x = exports('x', x * 2);
+			x = exports('x', x / 2);
+			x = exports('x', x % 2);
+			x = exports('x', x ** 2);
+			x = exports('x', x << 1);
+			x = exports('x', x >> 1);
+			x = exports('x', x >>> 1);
+			x = exports('x', x & 3);
+			x = exports('x', x ^ 2);
+			x = exports('x', x | 2);
+
+		}
+	};
+});
diff --git a/test/form/samples/updating-assignments/_expected/umd.js b/test/form/samples/updating-assignments/_expected/umd.js
new file mode 100644
index 00000000000..7500d5fd59f
--- /dev/null
+++ b/test/form/samples/updating-assignments/_expected/umd.js
@@ -0,0 +1,24 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
+	typeof define === 'function' && define.amd ? define(['exports'], factory) :
+	(global = global || self, factory(global.bundle = {}));
+}(this, (function (exports) { 'use strict';
+
+	exports.x = 1;
+	exports.x = 2;
+	exports.x += 1;
+	exports.x -= 1;
+	exports.x *= 2;
+	exports.x /= 2;
+	exports.x %= 2;
+	exports.x **= 2;
+	exports.x <<= 1;
+	exports.x >>= 1;
+	exports.x >>>= 1;
+	exports.x &= 3;
+	exports.x ^= 2;
+	exports.x |= 2;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+})));
diff --git a/test/form/samples/updating-assignments/main.js b/test/form/samples/updating-assignments/main.js
new file mode 100644
index 00000000000..fe7d0c7cde5
--- /dev/null
+++ b/test/form/samples/updating-assignments/main.js
@@ -0,0 +1,14 @@
+export let x = 1;
+x = 2;
+x += 1;
+x -= 1;
+x *= 2;
+x /= 2;
+x %= 2;
+x **= 2;
+x <<= 1;
+x >>= 1;
+x >>>= 1;
+x &= 3;
+x ^= 2;
+x |= 2;