diff --git a/analysis/tasks/FastProd.py b/analysis/tasks/FastProd.py
index af96b0037c47a465d069c6ae79d71459f3286451..1d3d5bd2582ca0a90848c65f2b5fa7426f142297 100644
--- a/analysis/tasks/FastProd.py
+++ b/analysis/tasks/FastProd.py
@@ -216,7 +216,7 @@ class FastProd(Task, TarballExtractionMixin, HTCondorWorkflow, law.LocalWorkflow
                     logger.debug(
                         "Job successful. Writing output tarfile from directory: %s", os.getcwd()
                     )
-                    self.output().dump(os.getcwd(), formatter="tar", add_kwargs=dict(filter=tarfilter))
+                    self.output().dump(os.getcwd(), mode="w:gz", formatter="tar", add_kwargs=dict(filter=tarfilter))
                 else:
                     debugfile = re.sub(
                         '.tar.gz$', '.debug.tar.gz', os.path.basename(self.output().path)
@@ -225,7 +225,7 @@ class FastProd(Task, TarballExtractionMixin, HTCondorWorkflow, law.LocalWorkflow
                         "Job failed. Writing debug tarfile: %s -> %s",
                         os.getcwd(), debugfile
                     )
-                    self.remote_target(debugfile).dump(os.getcwd(), formatter="tar")
+                    self.remote_target(debugfile).dump(os.getcwd(), mode="w:gz", formatter="tar")
 
             logger.debug("Removing temporary directory: %s", tmpdirpath)
             shutil.rmtree(tmpdirpath)
diff --git a/analysis/tasks/FastWarm.py b/analysis/tasks/FastWarm.py
index 95f915ccf59719c7edc23573806a274a6d1ff30b..e9d63cb06b58f51ddd8be9c515e2f5e5acd5501c 100644
--- a/analysis/tasks/FastWarm.py
+++ b/analysis/tasks/FastWarm.py
@@ -203,7 +203,7 @@ class FastWarm(Task, TarballExtractionMixin, HTCondorWorkflow, law.LocalWorkflow
                     logger.debug(
                         "Job successful. Writing output tarfile from directory: %s", os.getcwd()
                     )
-                    self.output().dump(os.getcwd(), formatter="tar", add_kwargs=dict(filter=tarfilter))
+                    self.output().dump(os.getcwd(), mode="w:gz", formatter="tar", add_kwargs=dict(filter=tarfilter))
                 else:
                     debugfile = re.sub(
                         '.tar.gz$', '.debug.tar.gz', os.path.basename(self.output().path)
@@ -212,7 +212,7 @@ class FastWarm(Task, TarballExtractionMixin, HTCondorWorkflow, law.LocalWorkflow
                         "Job failed. Writing debug tarfile: %s -> %s",
                         os.getcwd(), debugfile
                     )
-                    self.remote_target(debugfile).dump(os.getcwd(), formatter="tar")
+                    self.remote_target(debugfile).dump(os.getcwd(), mode="w:gz", formatter="tar")
 
             logger.debug("Removing temporary directory: %s", tmpdirpath)
             shutil.rmtree(tmpdirpath)
diff --git a/analysis/tasks/MergeFastWarm.py b/analysis/tasks/MergeFastWarm.py
index d6618345e9dbb4fdd52f9bbe9645cf6a98cd9ec6..1dcd8ea4bba82983ef0c0942706ff0663f6d41ed 100644
--- a/analysis/tasks/MergeFastWarm.py
+++ b/analysis/tasks/MergeFastWarm.py
@@ -144,7 +144,7 @@ class MergeFastWarm(Task, TarballExtractionMixin, HTCondorRemoteStorageMixin):
                     logger.debug(
                         "Job successful. Writing output tarfile from directory: %s", os.getcwd()
                     )
-                    self.output().dump(os.getcwd(), formatter="tar", add_kwargs=dict(filter=tarfilter))
+                    self.output().dump(os.getcwd(), mode="w:gz", formatter="tar", add_kwargs=dict(filter=tarfilter))
                 else:
                     debugfile = re.sub(
                         '.tar.gz$', '.debug.tar.gz', os.path.basename(self.output().path)
@@ -153,7 +153,7 @@ class MergeFastWarm(Task, TarballExtractionMixin, HTCondorRemoteStorageMixin):
                         "Job failed. Writing debug tarfile: %s -> %s",
                         os.getcwd(), debugfile
                     )
-                    self.remote_target(debugfile).dump(os.getcwd(), formatter="tar")
+                    self.remote_target(debugfile).dump(os.getcwd(), mode="w:gz", formatter="tar")
 
             logger.debug("Removing temporary directory: %s", tmpdirpath)
             shutil.rmtree(tmpdirpath)
diff --git a/analysis/tasks/Warmup.py b/analysis/tasks/Warmup.py
index 636a61a632d6dfebf3938d8a428e785b9ab3e84d..ca27a6c013499f2381a88d624d25ec618ce4b916 100644
--- a/analysis/tasks/Warmup.py
+++ b/analysis/tasks/Warmup.py
@@ -199,12 +199,12 @@ class Warmup(Task, TarballExtractionMixin, HTCondorWorkflow, law.LocalWorkflow):
 
                     logger.debug("Job successful. Writing output tarfile from directory: %s", os.getcwd())
                     logger.debug("Job successful. Writing output tarfile to directory: %s", self.output().path)
-                    self.output().dump(os.getcwd(), formatter="tar", add_kwargs=dict(filter=tarfilter))
+                    self.output().dump(os.getcwd(), mode="w:gz", formatter="tar", add_kwargs=dict(filter=tarfilter))
                 else:
                     if self.htcondor_remote_storage:
                         debugfile = re.sub('.tar.gz$', '.debug.tar.gz', os.path.basename(self.output().path))
                         logger.debug("Job failed. Writing debug tarfile: %s -> %s", os.getcwd(), debugfile)
-                        self.remote_target(debugfile).dump(os.getcwd(), formatter="tar")
+                        self.remote_target(debugfile).dump(os.getcwd(), mode="w:gz", formatter="tar")
 
             logger.debug("Removing temporary directory: %s", tmpdirpath)
             shutil.rmtree(tmpdirpath)