diff --git a/src/madness/chem/molecule.h b/src/madness/chem/molecule.h
index 341401c86f4..5ad20a5cf62 100644
--- a/src/madness/chem/molecule.h
+++ b/src/madness/chem/molecule.h
@@ -219,7 +219,7 @@ class Molecule {
 //            }
 
             if (source_type()=="xyz") set_derived_value("units",std::string("angstrom"));
-            if (units()=="bohr" or units()=="au") set_derived_value("units","atomic");
+            if (units()=="bohr" or units()=="au") set_derived_value("units",std::string("atomic"));
         }
 
         std::string source_type() const {return get<std::string>("source_type");}
@@ -543,4 +543,4 @@ class Molecule {
 
 }
 
-#endif
\ No newline at end of file
+#endif