diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 219b60c44a8..a54ebdcf388 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -580,7 +580,12 @@ struct curlFileTransfer : public FileTransfer
         #endif
 
         #if __linux__
-        unshareFilesystem();
+        try {
+            tryUnshareFilesystem();
+        } catch (nix::Error & e) {
+            e.addTrace({}, "in download thread");
+            throw;
+        }
         #endif
 
         std::map<CURL *, std::shared_ptr<TransferItem>> items;
diff --git a/src/libutil/linux/namespaces.cc b/src/libutil/linux/namespaces.cc
index f8289ef39c4..d4766cbba91 100644
--- a/src/libutil/linux/namespaces.cc
+++ b/src/libutil/linux/namespaces.cc
@@ -137,10 +137,10 @@ void restoreMountNamespace()
     }
 }
 
-void unshareFilesystem()
+void tryUnshareFilesystem()
 {
-    if (unshare(CLONE_FS) != 0 && errno != EPERM)
-        throw SysError("unsharing filesystem state in download thread");
+    if (unshare(CLONE_FS) != 0 && errno != EPERM && errno != ENOSYS)
+        throw SysError("unsharing filesystem state");
 }
 
 }
diff --git a/src/libutil/linux/namespaces.hh b/src/libutil/linux/namespaces.hh
index ef3c9123fbe..208920b80b1 100644
--- a/src/libutil/linux/namespaces.hh
+++ b/src/libutil/linux/namespaces.hh
@@ -20,11 +20,13 @@ void saveMountNamespace();
 void restoreMountNamespace();
 
 /**
- * Cause this thread to not share any FS attributes with the main
+ * Cause this thread to try to not share any FS attributes with the main
  * thread, because this causes setns() in restoreMountNamespace() to
  * fail.
+ *
+ * This is best effort -- EPERM and ENOSYS failures are just ignored.
  */
-void unshareFilesystem();
+void tryUnshareFilesystem();
 
 bool userNamespacesSupported();