diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 434a3981461..04fc21e60e0 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -1797,6 +1797,10 @@ namespace FourSlash {
                 // this.languageService.getScriptLexicalStructure(fileName);
             }
 
+            if (this.currentCaretPosition < 0) {
+                this.currentCaretPosition = 0;
+            }
+
             if (isFormattingEdit) {
                 const newContent = this.getFileContent(fileName);