diff --git a/DataFormats/EcalDigi/src/classes_def.xml b/DataFormats/EcalDigi/src/classes_def.xml
index 22036e9446e87..e84ce6e755cb1 100644
--- a/DataFormats/EcalDigi/src/classes_def.xml
+++ b/DataFormats/EcalDigi/src/classes_def.xml
@@ -148,6 +148,8 @@
    <class name="edm::Wrapper<edm::SortedCollection<EcalMatacqDigi,edm::StrictWeakOrdering<EcalMatacqDigi> > >" id="09B54EAE-7A1A-B892-117A-EFE5E32AF982"/>
 
    <class name="EcalDataArray"/>
+   <!-- ::Layout alias must be listed before the aliased-to type -->
+   <class name="EcalDigiHostCollection::Layout"/>
    <class name="EcalDigiSoA"/>
    <class name="EcalDigiSoA::View"/>
    <class name="EcalDigiHostCollection" ClassVersion="3">
@@ -156,6 +158,8 @@
    <class name="edm::Wrapper<EcalDigiHostCollection>" splitLevel="0"/>
 
    <class name="EcalDataArrayPhase2"/>
+   <!-- ::Layout alias must be listed before the aliased-to type -->
+   <class name="EcalDigiPhase2HostCollection::Layout"/>
    <class name="EcalDigiPhase2SoA"/>
    <class name="EcalDigiPhase2SoA::View"/>
    <class name="EcalDigiPhase2HostCollection" ClassVersion="3">