diff --git a/bids/layout/layout.py b/bids/layout/layout.py
index 44b73c892..c53b1f816 100644
--- a/bids/layout/layout.py
+++ b/bids/layout/layout.py
@@ -207,7 +207,7 @@ def __repr__(self):
                 (t.value, t.file.entities.get('subject'))
                  for t in
                  self.session.query(Tag).filter_by(entity_name='run')
-                 if t.file.entities.get('subject')
+                 if isinstance(t.value, int) and t.file.entities.get('subject')
                  )
             )
 
diff --git a/bids/tests/data/7t_trt/sub-01/ses-1/sub-01_ses-1_scans.json b/bids/tests/data/7t_trt/sub-01/ses-1/sub-01_ses-1_scans.json
new file mode 100644
index 000000000..7d975db95
--- /dev/null
+++ b/bids/tests/data/7t_trt/sub-01/ses-1/sub-01_ses-1_scans.json
@@ -0,0 +1,5 @@
+{
+	"run": {
+		"Description": "metadata to cause #681"
+	}
+}
\ No newline at end of file