diff --git a/code/IFCReaderGen.cpp b/code/IFCReaderGen.cpp
index 2895e05cc..5c0e5fafb 100644
--- a/code/IFCReaderGen.cpp
+++ b/code/IFCReaderGen.cpp
@@ -3695,7 +3695,7 @@ template <> size_t GenericFill<IfcRelContainedInSpatialStructure>(const DB& db,
 	if (params.GetSize() < 6) { throw STEP::TypeError("expected 6 arguments to IfcRelContainedInSpatialStructure"); }    do { // convert the 'RelatedElements' argument
         const DataType* arg = params[base++];
         try { GenericConvert( in->RelatedElements, *arg, db ); break; } 
-        catch (const TypeError& t) { throw TypeError(t.what() + std::string(" - expected argument 4 to IfcRelContainedInSpatialStructure to be a `SET [1:?] OF IfcProduct`")); }
+        catch (const TypeError& t) { throw TypeError(t.what() + std::string(" - expected argument 4 to IfcRelContainedInSpatialStructure to be a `SET [0:?] OF IfcProduct`")); }
     } while(0);
     do { // convert the 'RelatingStructure' argument
         const DataType* arg = params[base++];
diff --git a/code/IFCReaderGen.h b/code/IFCReaderGen.h
index d2f979e46..3101adf4c 100644
--- a/code/IFCReaderGen.h
+++ b/code/IFCReaderGen.h
@@ -3113,7 +3113,7 @@ namespace IFC {
 
     // C++ wrapper for IfcRelContainedInSpatialStructure
     struct IfcRelContainedInSpatialStructure : IfcRelConnects, ObjectHelper<IfcRelContainedInSpatialStructure,2> { IfcRelContainedInSpatialStructure() : Object("IfcRelContainedInSpatialStructure") {}
-		ListOf< Lazy< IfcProduct >, 1, 0 > RelatedElements;
+		ListOf< Lazy< IfcProduct >, 0, 0 > RelatedElements;
 		Lazy< IfcSpatialStructureElement > RelatingStructure;
     };