diff --git a/lib/spring/server.rb b/lib/spring/server.rb
index 91ea84ea..bfde1ee2 100644
--- a/lib/spring/server.rb
+++ b/lib/spring/server.rb
@@ -81,7 +81,12 @@ def rails_env_for(args, default_rails_env)
     # This will cause it to be automatically killed once the session
     # ends (i.e. when the user closes their terminal).
     def set_pgid
-      Process.setpgid(0, SID.pgid)
+      pgid = SID.pgid
+      if pgid.nil?
+        log "warn: unable to fetch process group of current session"
+        return
+      end
+      Process.setpgid(0, pgid)
     end
 
     # Ignore SIGINT and SIGQUIT otherwise the user typing ^C or ^\ on the command line
diff --git a/lib/spring/sid.rb b/lib/spring/sid.rb
index 1e0e8f69..581bcde9 100644
--- a/lib/spring/sid.rb
+++ b/lib/spring/sid.rb
@@ -36,7 +36,10 @@ def self.sid
     end
 
     def self.pgid
-      Process.getpgid(sid)
-    end
+      begin
+        Process.getpgid(sid)
+      rescue
+      end
+     end
   end
 end