diff --git a/src/jquery.flot.js b/src/jquery.flot.js
index d0b9af0..e992b2b 100644
--- a/src/jquery.flot.js
+++ b/src/jquery.flot.js
@@ -3067,7 +3067,7 @@ Licensed under the MIT license.
         }
 
         function drawSeriesPoints(series, i) {
-            function plotPoints(datapoints, radius, fillStyle, offset, shadow, axisx, axisy, symbol, extraData = null, t) {
+            function plotPoints(datapoints, radius, fillStyle, offset, shadow, axisx, axisy, symbol, extraData = null, t = 0) {
                 var points = datapoints.points, ps = datapoints.pointsize;
 
                 for (var i = 0; i < points.length; i += ps) {