diff --git a/doc/source/changes/version_0_35_1.rst.inc b/doc/source/changes/version_0_35_1.rst.inc
index 0066145..c3ea7c6 100644
--- a/doc/source/changes/version_0_35_1.rst.inc
+++ b/doc/source/changes/version_0_35_1.rst.inc
@@ -69,6 +69,9 @@ Fixes
 * do not try to display Path objects which point to a file or directory which
   does not exist (closes :editor_issue:`317`).
 
+* fixed (Excel) Sheet objects being only partially displayed when
+  the first value contains a number but other values contain text.
+
 * fixed the mechanism writing warning/error messages happening during the
   editor initialization. The errors are now correctly written in the user
   TEMP directory / larray-editor-stderr.log
\ No newline at end of file
diff --git a/larray_editor/arrayadapter.py b/larray_editor/arrayadapter.py
index 1a0a34a..97db2ac 100644
--- a/larray_editor/arrayadapter.py
+++ b/larray_editor/arrayadapter.py
@@ -1805,8 +1805,11 @@ def open(cls, fpath):
     def close(self):
         self.data.close()
 
-
-none_to_empty_string = np.vectorize(lambda v: v if v is not None else '')
+# we need to specify otypes explicitly here because otherwise np.vectorize
+# will use the type of the first value (e.g. int64) for the resulting array and that breaks if it
+# cannot hold subsequent values
+none_to_empty_string = np.vectorize(lambda v: v if v is not None else '',
+                                    otypes=[object])
 
 
 @adapter_for('larray.inout.xw_excel.Sheet')
@@ -2848,6 +2851,8 @@ class PyTablesFileAdapter(AbstractColumnarAdapter):
     _COLNAMES = ['Name']
 
     def __init__(self, data, attributes):
+        if not data.isopen:
+            raise ValueError('file is already closed')
         super().__init__(data=data, attributes=attributes)
 
     def shape2d(self):