null: fix string formatting

1 files changed, 2 insertions, 2 deletions

diff --git a/null.py b/null.py
index eb49c4d..13ed6d2 100644
--- a/null.py
+++ b/null.py
@@ -109,7 +109,7 @@ def _null_geodesic_kernel(times, t0, events, pu_t_0,
     if t0 < times[-1]:
         sol = solve_ivp(**args)
         if sol.status != 1:
-            raise ValueError('solver status from t0=%g: %d' % t0, sol.status)
+            raise ValueError('solver status from t0=%g: %d' % (t0, sol.status))
 
         sol_fwd = sol.sol
 
@@ -118,7 +118,7 @@ def _null_geodesic_kernel(times, t0, events, pu_t_0,
         args['t_span'] = (0.0, -1e6)
         sol = solve_ivp(**args)
         if sol.status != 1:
-            raise ValueError('solver status from t0=%g: %d' % t0, sol.status)
+            raise ValueError('solver status from t0=%g: %d' % (t0, sol.status))
 
         sol_back = sol.sol