diff --git a/pspy/so_map.py b/pspy/so_map.py
index 15c7302..3248d94 100644
--- a/pspy/so_map.py
+++ b/pspy/so_map.py
@@ -152,7 +152,7 @@ def get_lmax_limit(self):
         if self.pixel == "HEALPIX":
             l_max_limit = 3 * self.nside - 1
         elif self.pixel == "CAR":
-            cdelt = self.data.wcs.wcs.cdelt[1]
+            cdelt = abs(self.data.wcs.wcs.cdelt[1])
             l_max_limit = 360 / cdelt / 4
         return l_max_limit