diff --git a/npm-package/CodeEditor.vue b/npm-package/CodeEditor.vue
index 11f71e6..bbd9b55 100644
--- a/npm-package/CodeEditor.vue
+++ b/npm-package/CodeEditor.vue
@@ -331,7 +331,10 @@ export default {
       const singleLineHeight = this.$refs.lineNums.firstChild.offsetHeight;
       const heightNum = parseInt(this.textareaHeight / singleLineHeight) - 1;
       // displayed lineNum
-      this.lineNum = this.height == "auto" ? lineNum : lineNum > heightNum ? lineNum : heightNum;
+      const displayedLineNum = this.height == "auto" ? lineNum : lineNum > heightNum ? lineNum : heightNum;
+      if (!isNaN(displayedLineNum)) {
+        this.lineNum = displayedLineNum;
+      }
     },
   },
   mounted() {