1 files changed, 14 insertions, 2 deletions
diff --git a/go/game/state.go b/go/game/state.go
index f6bcbc8e..b72da192 100644
--- a/go/game/state.go
+++ b/go/game/state.go
@@ -458,6 +458,14 @@ func (s *LocalState) pushAction(a Action) {
 	s.stack.push(a)
 }
 
+type ErrDeclareSlowAction struct {
+	reason string
+}
+
+func (err ErrDeclareSlowAction) Error() string {
+	return err.reason
+}
+
 func (s *LocalState) declareAction(a Action) {
 	var err error
 
@@ -471,8 +479,12 @@ func (s *LocalState) declareAction(a Action) {
 			}
 		case *FreeAction:
 		default:
-			if a.Speed() == ActionSpeeds.Slow && !s.stack.IsEmpty() {
-				err = errors.New("slow action can not be declared while other actions are on the stack")
+			if a.Speed() == ActionSpeeds.Slow {
+				if !s.stack.IsEmpty() {
+					err = ErrDeclareSlowAction{"stack not empty"}
+				} else if s.activePlayerId != a.Controller().Id || s.activePhase != Phases.ActionPhase {
+					err = ErrDeclareSlowAction{"not action phase"}
+				}
 			}
 		}
 	}