diff --git a/tools/docs/placeholder.py b/tools/docs/placeholder.py
index 7fc3b485..a93af07e 100644
--- a/tools/docs/placeholder.py
+++ b/tools/docs/placeholder.py
@@ -20,8 +20,8 @@
 
 
 PLACEHOLDER = """placeholders:
-  IPYVIZZU_MINOR_VERSION: {}
-  LIB_MINOR_VERSION: {}
+  IPYVIZZU_MINOR_VERSION: "{}"
+  LIB_MINOR_VERSION: "{}"
 settings:
   auto_placeholder_tables: false
 """