diff --git a/src/signature_pad.js b/src/signature_pad.js
index 65bc7b8e..7f2da0de 100644
--- a/src/signature_pad.js
+++ b/src/signature_pad.js
@@ -154,6 +154,13 @@ SignaturePad.prototype._strokeBegin = function (event) {
 };
 
 SignaturePad.prototype._strokeUpdate = function (event) {
+  if (this._data.length === 0) {
+      // This can happen if clear() was called while a signature is still in progress,
+      // or if there is a race condition between start/update events.
+      this._strokeBegin(event)
+      return
+  }
+  
   const x = event.clientX;
   const y = event.clientY;