diff --git a/src/ast/nodes/AssignmentExpression.ts b/src/ast/nodes/AssignmentExpression.ts
index 3b0f57aa7b7..e30ccf7aa1e 100644
--- a/src/ast/nodes/AssignmentExpression.ts
+++ b/src/ast/nodes/AssignmentExpression.ts
@@ -76,7 +76,8 @@ export default class AssignmentExpression extends NodeBase {
 			this.right.render(code, options, {
 				renderedParentType: renderedParentType || this.parent.type
 			});
-			code.remove(this.start, this.right.start);
+			const operatorPos = findFirstOccurrenceOutsideComment(code.original, '=', this.left.end);
+			code.remove(this.start, findNonWhiteSpace(code.original, operatorPos + 1));
 		}
 		if (options.format === 'system') {
 			const exportNames =
diff --git a/src/utils/renderHelpers.ts b/src/utils/renderHelpers.ts
index 28021367797..a52ba90c62f 100644
--- a/src/utils/renderHelpers.ts
+++ b/src/utils/renderHelpers.ts
@@ -50,11 +50,12 @@ export function findFirstOccurrenceOutsideComment(code: string, searchString: st
 	}
 }
 
-const WHITESPACE = /\s/;
+const NON_WHITESPACE = /\S/g;
 
 export function findNonWhiteSpace(code: string, index: number) {
-	while (index < code.length && WHITESPACE.test(code[index])) index++;
-	return index;
+	NON_WHITESPACE.lastIndex = index;
+	const result = NON_WHITESPACE.exec(code)!;
+	return result.index;
 }
 
 // This assumes "code" only contains white-space and comments
diff --git a/test/function/samples/unused-parenthesed-assignment/_config.js b/test/function/samples/unused-parenthesed-assignment/_config.js
new file mode 100644
index 00000000000..24d8c766197
--- /dev/null
+++ b/test/function/samples/unused-parenthesed-assignment/_config.js
@@ -0,0 +1,6 @@
+module.exports = {
+	description: 'correctly simplifies assignments with right-hand-sides in parentheses (#3924)',
+	context: {
+		someObject: { isTrue: true }
+	}
+};
diff --git a/test/function/samples/unused-parenthesed-assignment/main.js b/test/function/samples/unused-parenthesed-assignment/main.js
new file mode 100644
index 00000000000..051552cb174
--- /dev/null
+++ b/test/function/samples/unused-parenthesed-assignment/main.js
@@ -0,0 +1,2 @@
+let unused = false;
+unused = (someObject.isTrue === true);