diff --git a/Projects/AnalysisBase/externals.txt b/Projects/AnalysisBase/externals.txt
index e9462a09585dccd4600992b5dee30bef54ed78db..b40776838a3a4bd52db6c38c132b355bc27ebdfa 100644
--- a/Projects/AnalysisBase/externals.txt
+++ b/Projects/AnalysisBase/externals.txt
@@ -1,4 +1,9 @@
 # Versions of the various externals to build before starting the build of
 # this project, when doing a full stack nightly build.
+#
+# Remember that when specifying the name of a branch, you *must* put
+# an "origin/" prefix before it. For tags however this is explicitly
+# forbidden.
 
-AnalysisBaseExternalsVersion = 6cbde55c
+# The version of atlas/atlasexternals to use:
+AnalysisBaseExternalsVersion = 3ddfb26b
diff --git a/Projects/AthSimulation/externals.txt b/Projects/AthSimulation/externals.txt
index 4d556447249e39c37fc55a4beb3436ed757d9cae..89d8bf56564554986389319b8434ddd080a41b6f 100644
--- a/Projects/AthSimulation/externals.txt
+++ b/Projects/AthSimulation/externals.txt
@@ -5,5 +5,8 @@
 # an "origin/" prefix before it. For tags however this is explicitly
 # forbidden.
 
-AthSimulationExternalsVersion = 6cbde55c
+# The version of atlas/atlasexternals to use:
+AthSimulationExternalsVersion = 3ddfb26b
+
+# The version of atlas/Gaudi to use:
 GaudiVersion = v28r2.005
diff --git a/Projects/Athena/externals.txt b/Projects/Athena/externals.txt
index 8e45acc7376cb08c0399161892d8233a1afdb5ba..c98dc6226d7c91fbab50a4217493b248ed4cfc88 100644
--- a/Projects/Athena/externals.txt
+++ b/Projects/Athena/externals.txt
@@ -5,5 +5,8 @@
 # an "origin/" prefix before it. For tags however this is explicitly
 # forbidden.
 
-AthenaExternalsVersion = 288f043b
+# The version of atlas/atlasexternals to use:
+AthenaExternalsVersion = 3ddfb26b
+
+# The version of atlas/Gaudi to use:
 GaudiVersion = v28r2.005