diff --git a/definitions/grib1/section.1.def b/definitions/grib1/section.1.def
index 244cbfc31..c4ee91b86 100644
--- a/definitions/grib1/section.1.def
+++ b/definitions/grib1/section.1.def
@@ -334,3 +334,10 @@ meta md5Product md5(offsetSection1,section1Length,gridDefinition,section1Flags,d
 
 # ECC-1806
 concept_nofail paramIdForConversion(zero, "paramIdForConversion.def", conceptsDir2, conceptsDir1) : long_type,read_only;
+
+if (productDefinitionTemplateNumber == 0 && defined(perturbationNumber) && numberOfForecastsInEnsemble > 0) {
+  alias productDefinitionTemplateNumber = one; # ensemble instant
+}
+if (productDefinitionTemplateNumber == 8 && defined(perturbationNumber) && numberOfForecastsInEnsemble > 0) {
+  alias productDefinitionTemplateNumber = eleven; # ensemble interval
+}