diff --git a/spacy/tokens/printers.py b/spacy/tokens/printers.py
index c7ae88f3d..16f4b5e08 100644
--- a/spacy/tokens/printers.py
+++ b/spacy/tokens/printers.py
@@ -37,8 +37,9 @@ def POS_tree(root, light=False, flat=False):
     `merge_ents(doc)` ran on it.
     """
     subtree = format_POS(root, light=light, flat=flat)
-    for c in root.children:
-        subtree["modifiers"].append(POS_tree(c))
+    if not flat:
+        for c in root.children:
+            subtree["modifiers"].append(POS_tree(c))
     return subtree