diff --git a/src/absil/ilreflect.fs b/src/absil/ilreflect.fs
index 337d07a2e15d..d9eaa83acab2 100644
--- a/src/absil/ilreflect.fs
+++ b/src/absil/ilreflect.fs
@@ -1721,7 +1721,7 @@ let rec buildTypeDefPass1 cenv emEnv (modB:ModuleBuilder) rootTypeBuilder nestin
     let typT =
         // Q: would it be ok to use typB :> Type ?
         // Maybe not, recall TypeBuilder maybe subtype of Type, but it is not THE Type.
-        let nameInModule = tref.QualifiedName
+        let nameInModule = tref.QualifiedName.Replace(",","\,")
         modB.GetTypeAndLog(nameInModule,false,false)
    
     let emEnv = envBindTypeRef emEnv tref (typT,typB,tdef)