diff --git a/shared/rascal/src/extract/RascalADT2BGF.rsc b/shared/rascal/src/extract/RascalADT2BGF.rsc
index 2a4559c5..ac366388 100644
--- a/shared/rascal/src/extract/RascalADT2BGF.rsc
+++ b/shared/rascal/src/extract/RascalADT2BGF.rsc
@@ -50,10 +50,10 @@ BGFGrammar process(loc src)
 	return normalise(syntax::BGF::grammar([],ps));
 }
 
-list[BGFProduction] def2prod((DataDef)`<Name n> = <DataExpr d> ;`)
-	= [production("","<n>",expr2expr(d))];
-default list[BGFProduction] def2prod((DataDef)`<Name n> = <{DataExpr "|"}+ ds> ;`)
-	= [production("","<n>",expr2expr(d)) | d <- ds];
+BGFProduction def2prod((DataDef)`<Name n> = <DataExpr d> ;`)
+	= production("","<n>",expr2expr(d));
+default BGFProduction def2prod((DataDef)`<Name n> = <{DataExpr "|"}+ ds> ;`)
+	= production("","<n>",choice([expr2expr(d) | d <- ds]));
 
 BGFExpression type2expr((Name)`str`) = val(string());
 BGFExpression type2expr((Name)`int`) = val(integer());
diff --git a/topics/convergence/guided/bgf/rascal-a.bgf b/topics/convergence/guided/bgf/rascal-a.bgf
index 21033eaf..bcbf71e3 100644
--- a/topics/convergence/guided/bgf/rascal-a.bgf
+++ b/topics/convergence/guided/bgf/rascal-a.bgf
@@ -1,2 +1,2 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<bgf:grammar xmlns:bgf="http://planet-sl.org/bgf"><bgf:production><label>prg</label><nonterminal>FLPrg</nonterminal><bgf:expression><selectable><selector>fs</selector><bgf:expression><star><bgf:expression><nonterminal>FLFun</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression></bgf:production><bgf:production><label>fun</label><nonterminal>FLFun</nonterminal><bgf:expression><sequence><bgf:expression><selectable><selector>f</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>args</selector><bgf:expression><star><bgf:expression><nonterminal>str</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>body</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></bgf:production><bgf:production><label>binary</label><nonterminal>FLExpr</nonterminal><bgf:expression><sequence><bgf:expression><selectable><selector>e1</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>op</selector><bgf:expression><nonterminal>FLOp</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>e2</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></bgf:production><bgf:production><label>apply</label><nonterminal>FLExpr</nonterminal><bgf:expression><sequence><bgf:expression><selectable><selector>f</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>vargs</selector><bgf:expression><star><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></bgf:production><bgf:production><label>ifThenElse</label><nonterminal>FLExpr</nonterminal><bgf:expression><sequence><bgf:expression><selectable><selector>c</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>t</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>e</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></bgf:production><bgf:production><label>argument</label><nonterminal>FLExpr</nonterminal><bgf:expression><selectable><selector>a</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression></bgf:production><bgf:production><label>literal</label><nonterminal>FLExpr</nonterminal><bgf:expression><selectable><selector>i</selector><bgf:expression><value>int</value></bgf:expression></selectable></bgf:expression></bgf:production><bgf:production><label>minus</label><nonterminal>FLOp</nonterminal><bgf:expression><epsilon /></bgf:expression></bgf:production><bgf:production><label>plus</label><nonterminal>FLOp</nonterminal><bgf:expression><epsilon /></bgf:expression></bgf:production><bgf:production><label>equal</label><nonterminal>FLOp</nonterminal><bgf:expression><epsilon /></bgf:expression></bgf:production></bgf:grammar>
+<bgf:grammar xmlns:bgf="http://planet-sl.org/bgf"><bgf:production><label>prg</label><nonterminal>FLPrg</nonterminal><bgf:expression><selectable><selector>fs</selector><bgf:expression><star><bgf:expression><nonterminal>FLFun</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression></bgf:production><bgf:production><label>fun</label><nonterminal>FLFun</nonterminal><bgf:expression><sequence><bgf:expression><selectable><selector>f</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>args</selector><bgf:expression><star><bgf:expression><nonterminal>str</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>body</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></bgf:production><bgf:production><nonterminal>FLExpr</nonterminal><bgf:expression><choice><bgf:expression><selectable><selector>binary</selector><bgf:expression><sequence><bgf:expression><selectable><selector>e1</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>op</selector><bgf:expression><nonterminal>FLOp</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>e2</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>apply</selector><bgf:expression><sequence><bgf:expression><selectable><selector>f</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>vargs</selector><bgf:expression><star><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></star></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>ifThenElse</selector><bgf:expression><sequence><bgf:expression><selectable><selector>c</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>t</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>e</selector><bgf:expression><nonterminal>FLExpr</nonterminal></bgf:expression></selectable></bgf:expression></sequence></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>argument</selector><bgf:expression><selectable><selector>a</selector><bgf:expression><value>string</value></bgf:expression></selectable></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>literal</selector><bgf:expression><selectable><selector>i</selector><bgf:expression><value>int</value></bgf:expression></selectable></bgf:expression></selectable></bgf:expression></choice></bgf:expression></bgf:production><bgf:production><nonterminal>FLOp</nonterminal><bgf:expression><choice><bgf:expression><selectable><selector>minus</selector><bgf:expression><epsilon /></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>plus</selector><bgf:expression><epsilon /></bgf:expression></selectable></bgf:expression><bgf:expression><selectable><selector>equal</selector><bgf:expression><epsilon /></bgf:expression></selectable></bgf:expression></choice></bgf:expression></bgf:production></bgf:grammar>