Index: wflow-py/wflow/wflowtools_lib.py
===================================================================
diff -u -rdfce1b75a3b16a10134c78a374885458d210a7b0 -rc1aa0272e0dd08f6595b31c1dce9f59b983459d8
--- wflow-py/wflow/wflowtools_lib.py	(.../wflowtools_lib.py)	(revision dfce1b75a3b16a10134c78a374885458d210a7b0)
+++ wflow-py/wflow/wflowtools_lib.py	(.../wflowtools_lib.py)	(revision c1aa0272e0dd08f6595b31c1dce9f59b983459d8)
@@ -1034,6 +1034,11 @@
     else:
         src = ds_in
     src_proj = src.GetProjection()
+    if not src_proj:
+        # assume a WGS 1984 projection
+        srs = osr.SpatialReference()
+        srs.ImportFromEPSG(4326)
+        src_proj = srs.ExportToWkt()
     if override_src_proj is not None:
         srs = osr.SpatialReference()
         srs.ImportFromEPSG(override_src_proj)