diff --git a/s2p/rpc_utils.py b/s2p/rpc_utils.py
index 350c01a9..c67f57c4 100644
--- a/s2p/rpc_utils.py
+++ b/s2p/rpc_utils.py
@@ -445,7 +445,7 @@ def exogenous_disp_range_estimation(rpc1, rpc2, x, y, w, h, H1, H2, cfg, A=None,
         disparity is made horizontal thanks to the two rectifying homographies
         H1 and H2.
     """
-    if cfg['exogenous_dem'] is None and cfg.get('exogenous_dem', None) in [None, False]:
+    if cfg['exogenous_dem'] is None and cfg.get('use_srtm', None) in [None, False]:
         return
 
     m, M = altitude_range(rpc1, x, y, w, h, cfg, margin_top, margin_bottom)