diff --git a/lapy/solver.py b/lapy/solver.py
index 5cbf9d8..5c17899 100644
--- a/lapy/solver.py
+++ b/lapy/solver.py
@@ -705,6 +705,8 @@ def poisson(self, h=0.0, dtup=(), ntup=()):  # poissonSolver
             raise ValueError(
                 "h should be either scalar or column vector with row num of A"
             )
+        if h.ndim == 1:
+            h = h[:,np.newaxis]
         # create vector d
         didx = []
         dvec = []