diff --git a/herbie/accessors.py b/herbie/accessors.py
index f8f0f4eb..99507f2e 100644
--- a/herbie/accessors.py
+++ b/herbie/accessors.py
@@ -56,6 +56,10 @@
 
 def add_proj_info(ds: xr.Dataset):
     """Add projection info to a Dataset."""
+    raise NotImplementedError("This function `add_proj_info` is not yet implemented.")
+
+    # TODO: remove pyproj dependency
+
     match = re.search(r'"source": "(.*?)"', ds.history)
     FILE = Path(match.group(1))