when trying to save a job with a copy artifact build step, a ClassNotFoundException is thrown:

java.lang.RuntimeException: Failed to instantiate class hudson.plugins.copyartifact.CopyArtifact from {"":"0","filter":"","flatten":false,"kind":"hudson.plugins.copyartifact.CopyArtifact$DescriptorImpl","optional":false,"projectName":"test","selector":

{"buildNumber":"35","fallback":false,"id":"","parameterName":"BUILD_SELECTOR","stableOnly":false,"stapler-class":["hudson.plugins.copyartifact.StatusBuildSelector","hudson.plugins.copyartifact.SavedBuildSelector","hudson.plugins.copyartifact.TriggeredBuildSelector","hudson.plugins.copyartifact.PermalinkBuildSelector","hudson.plugins.copyartifact.SpecificBuildSelector","hudson.plugins.copyartifact.WorkspaceSelector","hudson.plugins.copyartifact.ParameterizedBuildSelector"]}

,"stapler-class":"hudson.plugins.copyartifact.CopyArtifact","target":""}
at hudson.model.Descriptor.newInstance(Descriptor.java:543)
at hudson.model.Descriptor.newInstancesFromHeteroList(Descriptor.java:818)
at hudson.model.Descriptor.newInstancesFromHeteroList(Descriptor.java:805)
at hudson.util.DescribableList.rebuildHetero(DescribableList.java:185)
at hudson.model.Project.submit(Project.java:197)
at hudson.model.FreeStyleProject.submit(FreeStyleProject.java:99)
...
Caused by: java.lang.ClassNotFoundException: ["hudson.plugins.copyartifact.StatusBuildSelector","hudson.plugins.copyartifact.SavedBuildSelector","hudson.plugins.copyartifact.TriggeredBuildSelector","hudson.plugins.copyartifact.PermalinkBuildSelector","hudson.plugins.copyartifact.SpecificBuildSelector","hudson.plugins.copyartifact.WorkspaceSelector","hudson.plugins.copyartifact.ParameterizedBuildSelector"]
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:642)
at java.lang.ClassLoader.loadClass(ClassLoader.java:660)
at java.lang.ClassLoader.loadClass(ClassLoader.java:626)
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:596)
... 67 more