diff --git a/asu/build.py b/asu/build.py
index 3c80ebd0..6fdd0448 100644
--- a/asu/build.py
+++ b/asu/build.py
@@ -271,7 +271,7 @@ def download_file(filename: str, dest: str = None):
 
     log.debug("Created store path: %s", req["store_path"] / bin_dir)
 
-    if "filesystem" in req:
+    if req.get("filesystem"):
         config_path = cache_workdir / ".config"
         config = config_path.read_text()
 
@@ -293,6 +293,7 @@ def download_file(filename: str, dest: str = None):
 
         config_path.write_text(config)
     else:
+        log.debug("Enable default filesystems")
         copyfile(
             cache_workdir / ".config.orig",
             cache_workdir / ".config",
diff --git a/asu/openapi.yml b/asu/openapi.yml
index 283a5be3..2d8af63f 100644
--- a/asu/openapi.yml
+++ b/asu/openapi.yml
@@ -260,6 +260,7 @@ components:
             - ext4
             - ubifs
             - jffs2
+            - ""
           description: |
             Ability to specify filesystem running on device. Attaching this
             optional parameter will limit the ImageBuilder to only build
diff --git a/tests/test_api.py b/tests/test_api.py
index c236bf57..57ed2ee0 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -62,6 +62,26 @@ def test_api_build_filesystem_squashfs(app, upstream):
     assert "# CONFIG_TARGET_ROOTFS_EXT4FS is not set" in config
     assert "CONFIG_TARGET_ROOTFS_SQUASHFS=y" in config
 
+def test_api_build_filesystem_empty(app, upstream):
+    client = app.test_client()
+    response = client.post(
+        "/api/v1/build",
+        json=dict(
+            version="TESTVERSION",
+            target="testtarget/testsubtarget",
+            profile="testprofile",
+            packages=["test1", "test2"],
+            filesystem="",
+        ),
+    )
+    assert response.status == "200 OK"
+    assert response.json.get("request_hash") == "33377fbd91c50c4236343f1dfd67f9ae"
+    config = (
+        app.config["CACHE_PATH"] / "cache/TESTVERSION/testtarget/testsubtarget/.config"
+    ).read_text()
+    assert "CONFIG_TARGET_ROOTFS_EXT4FS=y" in config
+    assert "CONFIG_TARGET_ROOTFS_SQUASHFS=y" in config
+
 
 def test_api_build_filesystem_reset(app, upstream):
     client = app.test_client()