diff --git a/mcdc/loop.py b/mcdc/loop.py
index c5913a4c..e219b004 100644
--- a/mcdc/loop.py
+++ b/mcdc/loop.py
@@ -395,7 +395,7 @@ def gmres(seed, mcdc):
     if normb == 0.0:
         normb = 1.0
     if normr < tol * normb:
-        return  X, 0
+        return X, 0
 
     iteration = 0
 
@@ -554,7 +554,7 @@ def power_iteration(seed, mcdc):
             mcdc["technique"]["iqmc_res_outter"] <= tol
         ):
             simulation_end = True
-        
+
         loop_index += numba.uint64(1)
 
     if mcdc["setting"]["progress_bar"]:
@@ -562,7 +562,6 @@ def power_iteration(seed, mcdc):
             print_iqmc_eigenvalue_exit_code(mcdc)
 
 
-
 @njit
 def davidson(seed, mcdc):
     """
diff --git a/test/regression/eigenvalue/slab_kornreich_iqmc/test.py b/test/regression/eigenvalue/slab_kornreich_iqmc/test.py
index e973cd55..e78cb4ad 100644
--- a/test/regression/eigenvalue/slab_kornreich_iqmc/test.py
+++ b/test/regression/eigenvalue/slab_kornreich_iqmc/test.py
@@ -3,8 +3,10 @@
 import mcdc
 
 import numba as nb
+
 nb.config.DISABLE_JIT = True
 
+
 def pi_test():
     # =========================================================================
     # Set model
@@ -161,7 +163,6 @@ def davidson_test():
     b = output["iqmc/flux"][:]
     assert np.allclose(a, b)
 
-
     a = output["k_eff"][()]
     b = answer["k_eff"][()]
     assert np.allclose(a, b)