diff --git a/xarrayfits/grid.py b/xarrayfits/grid.py
index 4a1cac2..4a5f34f 100644
--- a/xarrayfits/grid.py
+++ b/xarrayfits/grid.py
@@ -29,11 +29,11 @@ def __init__(self, header: Mapping):
 
         self._grid = []
 
-        for d in range(ndims):
-            pixels = np.arange(1, self._naxis[d] + 1, dtype=np.float64)
-            self._grid.append(
-                (pixels - self._crpix[d]) * self._cdelt[d] + self._crval[d]
-            )
+        for na, rp, dt, rv in enumerate(
+            zip(self._naxis, self._crpix, self._cdelt, self._crval)
+        ):
+            pixels = np.arange(1, na + 1, dtype=np.float64)
+            self._grid.append((pixels - rp) * dt + rv)
 
     @property
     def naxis(self):