diff --git a/src/productcomposer/wrappers/modifyrepo.py b/src/productcomposer/wrappers/modifyrepo.py
index 99626f8..3da887d 100644
--- a/src/productcomposer/wrappers/modifyrepo.py
+++ b/src/productcomposer/wrappers/modifyrepo.py
@@ -1,3 +1,5 @@
+import os
+
 from pydantic.types import DirectoryPath
 from pydantic.types import FilePath
 
@@ -14,8 +16,8 @@ class ModifyrepoWrapper(BaseWrapper):
     mdtype: str | None = Field()
 
     def get_cmd(self):
-        directory = os.path.join(self.directory, "repodata")
-        cmd = ["modify", self.file, directory]
+        directory = self.directory / "repodata"
+        cmd = ["modifyrepo", self.file.as_posix(), directory.as_posix()]
 
         cmd.append("--unique-md-filenames")
         cmd.append(f"--checksum={self.checksum_type}")