diff --git a/src/setuptools_dso/dsocmd.py b/src/setuptools_dso/dsocmd.py
index e9482e5..44ef178 100644
--- a/src/setuptools_dso/dsocmd.py
+++ b/src/setuptools_dso/dsocmd.py
@@ -220,7 +220,7 @@ def dso2lib_pre(self, ext):
             try:
                 # also check if this DSO lives in an external package.
                 for i in range(1, len(parts)):
-                    basepackage = import_module(".".join(parts[0:i])).__file__
+                    basepackage = getattr(import_module(".".join(parts[0:i])), "__file__", None)
                     if basepackage:
                         dsobase = os.path.dirname(basepackage)
                         if i < len(parts):