diff --git a/src/main/java/be/cylab/java/wowa/training/Utils.java b/src/main/java/be/cylab/java/wowa/training/Utils.java
index 5681f3de7ed628c78747fb8d23cf593aa4ee41d9..e8174f4be434425d68cfa1251cd77d97b3f8d493 100644
--- a/src/main/java/be/cylab/java/wowa/training/Utils.java
+++ b/src/main/java/be/cylab/java/wowa/training/Utils.java
@@ -472,7 +472,7 @@ final class Utils {
             final double wowa_accuracy,
             final double wowa_f_1) {
         try (OutputStreamWriter writer = new OutputStreamWriter(
-                new FileOutputStream(filename),
+                new FileOutputStream(filename, true),
                 StandardCharsets.UTF_8)) {
 
             writer.write("___________________________________________\n");
@@ -531,7 +531,7 @@ final class Utils {
             final double average_accuracy,
             final double average_f_1) {
         try (OutputStreamWriter writer = new OutputStreamWriter(
-                new FileOutputStream(filename),
+                new FileOutputStream(filename, true),
                 StandardCharsets.UTF_8)) {
 
             writer.write("___________________________________________\n");