diff --git a/osbuild/util/bls.py b/osbuild/util/bls.py
new file mode 100644
index 00000000..c4922bec
--- /dev/null
+++ b/osbuild/util/bls.py
@@ -0,0 +1,34 @@
+"""
+Function for appending parameters to
+Boot Loader Specification (BLS).
+"""
+import glob
+from typing import List
+
+
+def options_append(root_path: str, kernel_arguments: List[str]) -> None:
+    """
+    Add kernel arguments to the Boot Loader Specification (BLS) configuration files.
+    There is unlikely to be more than one BLS config, but just in case, we'll iterate over them.
+
+    Parameters
+    ----------
+
+    root_path (str): The root path for locating BLS configuration files.
+    kernel_arguments (list): A list of kernel arguments to be added.
+
+    """
+    bls_glob = f"{root_path}/loader/entries/*.conf"
+    bls_conf_files = glob.glob(bls_glob)
+    if len(bls_conf_files) == 0:
+        raise RuntimeError(f"no BLS configuration found in {bls_glob}")
+    for entry in bls_conf_files:
+        # Read in the file and then append to the options line.
+        with open(entry, encoding="utf8") as f:
+            lines = f.read().splitlines()
+        with open(entry, "w", encoding="utf8") as f:
+            for line in lines:
+                if line.startswith('options '):
+                    f.write(f"{line} {' '.join(kernel_arguments)}\n")
+                else:
+                    f.write(f"{line}\n")
diff --git a/stages/org.osbuild.kernel-cmdline.bls-append b/stages/org.osbuild.kernel-cmdline.bls-append
index dd166624..9b9006a0 100755
--- a/stages/org.osbuild.kernel-cmdline.bls-append
+++ b/stages/org.osbuild.kernel-cmdline.bls-append
@@ -7,11 +7,11 @@ the tree or in a mount.
 """
 
 
-import glob
 import sys
 from urllib.parse import urlparse
 
 import osbuild.api
+from osbuild.util import bls
 
 SCHEMA_2 = r"""
 "options": {
@@ -60,24 +60,7 @@ def main(paths, tree, options):
 
     assert url.path.startswith("/")
     bootroot = root + url.path
-
-    # There is unlikely to be more than one bls config, but just
-    # in case we'll iterate over them.
-    entries = []
-    for entry in glob.glob(f"{bootroot}/loader/entries/*.conf"):
-        entries.append(entry)
-        # Read in the file and then append to the options line.
-        with open(entry, encoding="utf8") as f:
-            lines = f.read().splitlines()
-        with open(entry, "w", encoding="utf8") as f:
-            for line in lines:
-                if line.startswith('options '):
-                    f.write(f"{line} {' '.join(kopts)}\n")
-                else:
-                    f.write(f"{line}\n")
-    assert len(entries) != 0
-    print(f"Added {','.join(kopts)} to: {','.join(entries)}")
-    return 0
+    bls.options_append(bootroot, kopts)
 
 
 if __name__ == '__main__':