diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 6d2d458da..a50fe1a28 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -910,7 +910,7 @@ void LocalDerivationGoal::startBuilder()
                after we've created the new user namespace. */
             if (settings.dropSupplementaryGroups)
                 if (setgroups(0, 0) == -1)
-                    throw SysError("setgroups failed");
+                    throw SysError("setgroups failed. Set the drop-supplementary-groups option to false to skip this step.");
 
             ProcessOptions options;
             options.cloneFlags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD;