diff --git a/asu/build.py b/asu/build.py
index 96c44681..0cedee8b 100644
--- a/asu/build.py
+++ b/asu/build.py
@@ -9,8 +9,12 @@
 import requests
 from rq import get_current_job
 
-from .common import (fingerprint_pubkey_usign, get_file_hash,
-                     get_packages_hash, verify_usign)
+from .common import (
+    fingerprint_pubkey_usign,
+    get_file_hash,
+    get_packages_hash,
+    verify_usign,
+)
 
 log = logging.getLogger("rq.worker")
 log.setLevel(logging.DEBUG)
@@ -338,6 +342,24 @@ def download_file(filename: str, dest: str = None):
     if "is too big" in image_build.stderr:
         report_error("Selected packages exceed device storage")
 
+    kernel_build_dir_run = subprocess.run(
+        ["make", "val.KERNEL_BUILD_DIR"],
+        text=True,
+        cwd=cache_workdir,
+        capture_output=True,
+    )
+
+    if kernel_build_dir_run.returncode:
+        report_error("Couldn't determine KERNEL_BUILD_DIR")
+
+    kernel_build_dir_tmp = Path(kernel_build_dir_run.stdout.strip()) / "tmp"
+
+    if kernel_build_dir_tmp.exists():
+        log.info("Removing KDIR_TMP at %s", kernel_build_dir_tmp)
+        rmtree(kernel_build_dir_tmp)
+    else:
+        log.warning("KDIR_TMP missing at %s", kernel_build_dir_tmp)
+
     json_file = Path(req["store_path"] / bin_dir / "profiles.json")
 
     if not json_file.is_file():
diff --git a/tests/test_api.py b/tests/test_api.py
index ea191313..2f8c0b89 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -518,3 +518,24 @@ def test_api_build_package_to_replace(client, upstream):
     )
     assert response.status == "200 OK"
     assert response.json.get("request_hash") == "8dd81d51057d322b46aa3739ccf4a8a6"
+
+
+def test_api_build_cleanup(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="ext4",
+        ),
+    )
+    assert response.status == "200 OK"
+    assert not (
+        app.config["CACHE_PATH"]
+        / "cache/TESTVERSION/testtarget/testsubtarget"
+        / "pseudo_kernel_build_dir/tmp/"
+        / "fake_trash"
+    ).exists()
diff --git a/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz b/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz
index 3277025a..254ae645 100644
Binary files a/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz and b/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz differ
diff --git a/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/Makefile b/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/Makefile
index 3cd7d9e1..625d4f9e 100644
--- a/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/Makefile
+++ b/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/Makefile
@@ -9,3 +9,6 @@ manifest:
 
 info:
 	@cat ./openwrt-testtarget-testsubtarget-testprofile.info
+
+val.KERNEL_BUILD_DIR:
+	@echo "$$(pwd)/pseudo_kernel_build_dir/"
diff --git a/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/pseudo_kernel_build_dir/tmp/fake_trash b/tests/upstream/snapshots/targets/testtarget/testsubtarget/openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64/pseudo_kernel_build_dir/tmp/fake_trash
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums b/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums
index b9edb4d8..35fe96fb 100644
--- a/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums
+++ b/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums
@@ -1 +1 @@
-f7a57262cde30d84db51d6db5b1eee16f5c0525e67f01dcbe10a9693e3c88fde *openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz
+4e645577d934129a65d0f79cf55d90e1199f5ab90ab27803cefae8badc868599 *openwrt-imagebuilder-testtarget-testsubtarget.Linux-x86_64.tar.xz
diff --git a/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums.sig b/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums.sig
index 9edfbf77..6999e851 100644
--- a/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums.sig
+++ b/tests/upstream/snapshots/targets/testtarget/testsubtarget/sha256sums.sig
@@ -1,2 +1,2 @@
 untrusted comment: verify with testkey.pub
-RWRqylWEtrAZQ/BrgCkjQaOak7bVi7CWfwKbK/rKK39w4e0l7jL+D23xAZZXS3Qb/x6jwulK3lbuCU61etNGaLE2KxWfk1hY4QM=
+RWRqylWEtrAZQwwqVGXn0U/Q3nnrboIdIVK2aW7Q8JMN3pmCzHa8o5MppWUqMhxh/h2Dc/3WUjVtWgvfDGrR0tJJ/Wauy9r7QwM=