diff --git a/src/main/java/org/aksw/gerbil/execute/AnnotatorOutputWriter.java b/src/main/java/org/aksw/gerbil/execute/AnnotatorOutputWriter.java
index 1ce9f5377..4542cfd54 100644
--- a/src/main/java/org/aksw/gerbil/execute/AnnotatorOutputWriter.java
+++ b/src/main/java/org/aksw/gerbil/execute/AnnotatorOutputWriter.java
@@ -88,7 +88,7 @@ private File generateOutputFile(ExperimentTaskConfiguration configuration) {
             fileBuilder.append("-s-");
         }
         appendCleanedString(fileBuilder, configuration.type.name());
-        fileBuilder.append(".ttl");
+        fileBuilder.append(".ttl.gz");
         return new File(fileBuilder.toString());
     }