diff --git a/s2p/rpc_utils.py b/s2p/rpc_utils.py
index c67f57c4..f0028e2a 100644
--- a/s2p/rpc_utils.py
+++ b/s2p/rpc_utils.py
@@ -111,7 +111,7 @@ def min_max_heights_from_bbx(im, lon_m, lon_M, lat_m, lat_M, rpc, exogenous_dem_
         vertical_datum = [x for x in proj_crs.sub_crs_list if x.is_vertical][0]
         crs_epsg = f"epsg:{horizontal_crs.to_epsg()}+{vertical_datum.to_epsg()}"
     else:
-        crs_epsg = proj_crs.to_epsg()
+        crs_epsg = f"epsg:{proj_crs.to_epsg()}"
     # convert lon/lat to im projection
     x_im_proj, y_im_proj = geographiclib.pyproj_transform([lon_m, lon_M],
                                                           [lat_m, lat_M],
diff --git a/setup.py b/setup.py
index 29416c3a..fa39f158 100644
--- a/setup.py
+++ b/setup.py
@@ -63,7 +63,7 @@ def finalize_options(self):
 }
 
 setup(name="s2p",
-      version="1.6.4",
+      version="1.6.5",
       description="Satellite Stereo Pipeline.",
       long_description=readme(),
       long_description_content_type='text/markdown',