diff --git a/archetypal/eplus_interface/expand_objects.py b/archetypal/eplus_interface/expand_objects.py
index 38efbf24..63ead176 100644
--- a/archetypal/eplus_interface/expand_objects.py
+++ b/archetypal/eplus_interface/expand_objects.py
@@ -54,7 +54,8 @@ def run(self):
 
             # Move files into place
             tmp = self.tmp
-            self.epw = self.idf.epw.copy(tmp / "in.epw").expand()
+            if self.idf.epw is not None:
+                self.epw = self.idf.epw.copy(tmp / "in.epw").expand()
             self.idfname = Path(self.idf.savecopy(tmp / "in.idf")).expand()
             self.idd = self.idf.iddname.copy(tmp / "Energy+.idd").expand()
             expand_object_exe = shutil.which("ExpandObjects", path=self.eplus_home)
diff --git a/requirements.txt b/requirements.txt
index 68b2719f..e3ead319 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -20,3 +20,4 @@ sklearn~=0.0
 CoolProp~=6.4.1
 energy-pandas~=0.3.3
 validator_collection~=1.5.0
+pint==0.19
\ No newline at end of file