diff --git a/segment/val.py b/segment/val.py
index 368a058f9ced..5cf8ae8b41c1 100644
--- a/segment/val.py
+++ b/segment/val.py
@@ -463,6 +463,8 @@ def main(opt):
                 np.savetxt(f, y, fmt='%10.4g')  # save
             os.system('zip -r study.zip study_*.txt')
             plot_val_study(x=x)  # plot
+        else:
+            raise NotImplementedError(f'--task {opt.task} not in ("train", "val", "test", "speed", "study")')
 
 
 if __name__ == "__main__":
diff --git a/val.py b/val.py
index e84249ed383f..8d27d9d3dab1 100644
--- a/val.py
+++ b/val.py
@@ -399,6 +399,8 @@ def main(opt):
                 np.savetxt(f, y, fmt='%10.4g')  # save
             os.system('zip -r study.zip study_*.txt')
             plot_val_study(x=x)  # plot
+        else:
+            raise NotImplementedError(f'--task {opt.task} not in ("train", "val", "test", "speed", "study")')
 
 
 if __name__ == "__main__":