diff --git a/shared/helpers.js b/shared/helpers.js
index 5cfa8b376..eb3dba6d8 100644
--- a/shared/helpers.js
+++ b/shared/helpers.js
@@ -163,7 +163,7 @@ const debugTextMismatch = (clientTextRaw, serverTextRaw, label)=>{
 			const getMismatchContext = (text, index, name, size = 10)=>{
 				const lower = Math.max(index - size, 0);
 				const upper = Math.min(index + size, text.length);
-				const slice = `${JSON.stringify(text.slice(lower, index - 1)).slice(1, -1)}\u001B[31m${JSON.stringify(text[i]).slice(1, -1)}\u001B[0m${JSON.stringify(text.slice(index+1, upper)).slice(1, -1)}`;
+				const slice = `${JSON.stringify(text.slice(lower, index)).slice(1, -1)}\u001B[31m${JSON.stringify(text[i]).slice(1, -1)}\u001B[0m${JSON.stringify(text.slice(index+1, upper)).slice(1, -1)}`;
 				const lineNo = text.slice(0, index).split('\n').length;
 				const code = `U+${text.charCodeAt(i).toString(16).toUpperCase()}`;