diff --git a/webgl.js b/webgl.js
index 9204f46e..9f1f722e 100644
--- a/webgl.js
+++ b/webgl.js
@@ -2728,6 +2728,10 @@ gl.isEnabled = function isEnabled (cap) {
 
 var _lineWidth = gl.lineWidth
 gl.lineWidth = function lineWidth (width) {
+  if (isNaN(width)) {
+    setError(this, gl.INVALID_VALUE)
+    return
+  }
   return _lineWidth.call(this, +width)
 }