diff --git a/datajoint/fetch.py b/datajoint/fetch.py
index 61a911ba5..4474482ac 100644
--- a/datajoint/fetch.py
+++ b/datajoint/fetch.py
@@ -280,6 +280,9 @@ def __getitem__(self, item):
         item, attributes = prepare_attributes(self._relation, item)
 
         result = self._relation.project(*attributes).fetch()
+        if len(result) != 1:
+            raise DataJointError('Fetch1 should only return one tuple')
+
         return_values = tuple(
             np.ndarray(result.shape,
                        np.dtype({name: result.dtype.fields[name] for name in self._relation.primary_key}),
diff --git a/datajoint/heading.py b/datajoint/heading.py
index 7a742416b..a08e3f3af 100644
--- a/datajoint/heading.py
+++ b/datajoint/heading.py
@@ -230,7 +230,7 @@ def project(self, *attribute_list, **renamed_attributes):
 
     def join(self, other, left):
         """
-        join two headings
+        Joins two headings.
         """
         assert isinstance(other, Heading)
         attribute_list = [v._asdict() for v in self.attributes.values()]
diff --git a/datajoint/relational_operand.py b/datajoint/relational_operand.py
index 3ee4e3bf4..f3e25b0d2 100644
--- a/datajoint/relational_operand.py
+++ b/datajoint/relational_operand.py
@@ -339,7 +339,7 @@ def from_clause(self):
 
     @property
     def select_fields(self):
-        return '*'
+        return self.heading.as_sql
 
 
 class Projection(RelationalOperand):