diff --git a/src/core/raster/qgsrasterlayer.cpp b/src/core/raster/qgsrasterlayer.cpp
index 9d8128dc981..1668d1308bc 100644
--- a/src/core/raster/qgsrasterlayer.cpp
+++ b/src/core/raster/qgsrasterlayer.cpp
@@ -1398,6 +1398,9 @@ bool QgsRasterLayer::writeSld( QDomNode &node, QDomDocument &doc, QString &error
           case QgsHueSaturationFilter::GrayscaleAverage:
             property = QStringLiteral( "average" );
             break;
+          case QgsHueSaturationFilter::GrayscaleOff:
+            // added just to avoid travis fail
+            break;
         }
         if ( !property.isEmpty() )
           vendorOptionWriter( QStringLiteral( "grayScale" ), property );