diff --git a/npbackup/configuration.py b/npbackup/configuration.py
index 548e49f..af203c5 100644
--- a/npbackup/configuration.py
+++ b/npbackup/configuration.py
@@ -164,7 +164,7 @@ empty_config_dict = {
                 "exclude_files_larger_than": None,
                 "additional_parameters": None,
                 "additional_backup_only_parameters": None,
-                "minimum_backup_size_error": "10",  # In megabytes
+                "minimum_backup_size_error": "10MiB",  # allows BytesConverter units
                 "pre_exec_commands": [],
                 "pre_exec_per_command_timeout": 3600,
                 "pre_exec_failure_is_fatal": False,
diff --git a/npbackup/restic_metrics/__init__.py b/npbackup/restic_metrics/__init__.py
index 3721195..e7fc6cc 100644
--- a/npbackup/restic_metrics/__init__.py
+++ b/npbackup/restic_metrics/__init__.py
@@ -168,7 +168,7 @@ def restic_str_output_to_json(
 
 
 def restic_json_to_prometheus(
-    restic_result: bool, restic_json: dict, labels: dict = None, minimum_backup_size_error: float = None,
+    restic_result: bool, restic_json: dict, labels: dict = None, minimum_backup_size_error: str = None,
 ) -> Tuple[bool, List[str], bool]:
     """
     Transform a restic JSON result into prometheus metrics
@@ -225,7 +225,7 @@ def restic_json_to_prometheus(
 
     backup_too_small = False
     if minimum_backup_size_error:
-        if restic_json["data_added"] < minimum_backup_size_error:
+        if restic_json["data_added"] < int(BytesConverter(str(minimum_backup_size_error).replace(" ", ""))):
             backup_too_small = True
     good_backup = restic_result and not backup_too_small