diff --git a/toolkit/content/about.js b/toolkit/content/about.js
index 6e655e247..44d0abf99 100644
--- a/toolkit/content/about.js
+++ b/toolkit/content/about.js
@@ -29,7 +29,7 @@ if (versionNum.substr(0,3) == "45.") {
   // FPR series
   var vf = 0 + versionNum.substr(3);
   var pl = ""+ (vf - (vf|0));
-  pl = (0 + pl.substr(1))|0;
+  pl = ((0 + pl.substr(1) * 10)+0.001)|0; // damn float rounding
   vf = vf|0; vf -= 9;
   // XXX localize me
   version.textContent = "Feature Parity Release "+vf+