diff --git a/go.mod b/go.mod
index cf5969c..72f9479 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,12 @@
 module github.com/IBM/nzgo/v12
 
-go 1.14
+go 1.15
 require(
         github.com/IBM/nzgo v11.1.0+incompatible
 )
+
+// Do not use these versions
+retract (
+	v12.0.2
+	v12.0.0
+)