diff --git a/bindings/python/wscript b/bindings/python/wscript
index 94ab85f98..1cc170a91 100644
--- a/bindings/python/wscript
+++ b/bindings/python/wscript
@@ -14,7 +14,13 @@ from waflib.Errors import WafError
 # after = TaskGen.after
 
 # https://github.com/gjcarneiro/pybindgen
-REQUIRED_PYBINDGEN_VERSION = '0.21.0'
+# If specifying a released pybindgen version, specify the required PYBINDGEN
+# version as, e.g. '0.21.0'
+# If specifying a commit on the development tree, specify it like this based
+# on 'git describe --tags' command.  Example, if the latest release was 0.21.0,
+# and 'git decribe --tags' reports "0.21.0-6-g8e7c0a9", then write the
+# PYBINDGEN version string below as '0.21.0.post6+ng8e7c0a9'
+REQUIRED_PYBINDGEN_VERSION = '0.21.0.post6+ng8e7c0a9'
 REQUIRED_PYGCCXML_VERSION = (1, 9, 1)
 REQUIRED_CASTXML_VERSION = '0.2'