Ouch... missed an equal sign.
diff --git a/tools/generator-polygene/app/templates/buildtool/gradle-root.tmpl b/tools/generator-polygene/app/templates/buildtool/gradle-root.tmpl
index 6ec2b7f..60dbb70 100644
--- a/tools/generator-polygene/app/templates/buildtool/gradle-root.tmpl
+++ b/tools/generator-polygene/app/templates/buildtool/gradle-root.tmpl
@@ -33,7 +33,7 @@
 <%
 }
 if( polygene.entitystore == 'DerbySQL'  ) {
-%>  derbyVersion "10.13.1.1"
+%>  derbyVersion = "10.13.1.1"
 <%
 }
 if( polygene.entitystore == 'H2SQL'  ) {