diff --git a/VECTO/OutputData/JSONFileWriter.vb b/VECTO/OutputData/JSONFileWriter.vb
index cd75ddf76eb4090ae86cb979ee68c3ce24f173c6..a5f76f078f9c783e6f8f7559e35e810e18bafb44 100644
--- a/VECTO/OutputData/JSONFileWriter.vb
+++ b/VECTO/OutputData/JSONFileWriter.vb
@@ -55,7 +55,7 @@ Public Class JSONFileWriter
 		body.Add("RatedPower", eng.RatedPowerDeclared.Value())
 		body.Add("RatedSpeed", eng.RatedSpeedDeclared.AsRPM)
 		body.Add("MaxTorque", eng.MaxTorqueDeclared.Value())
-		body.Add("FuelType", eng.FuelType)
+		body.Add("FuelType", eng.FuelType.ToString())
 
 		body.Add("FullLoadCurve", GetRelativePath(eng.FullLoadCurve.Source, Path.GetDirectoryName(filename)))