diff --git a/.ci/testcases/test_source.py b/.ci/testcases/test_source.py
index a9a3d0ca8..8fb7086e3 100644
--- a/.ci/testcases/test_source.py
+++ b/.ci/testcases/test_source.py
@@ -4,9 +4,10 @@
 # Various checks on source= in the APKBUILDs
 
 import glob
+import logging
+import os
 import pytest
 import sys
-import os
 
 import add_pmbootstrap_to_import_path
 import pmb.parse
@@ -102,3 +103,50 @@ def test_aports_unreferenced_files(args):
                     and rel_file_path not in subpackage_installs \
                     and rel_file_path not in trigger_sources:
                 raise RuntimeError(f"{apkbuild_path}: found unreferenced file: {rel_file_path}")
+
+
+def test_distfiles_conflict(args):
+    """
+    Make sure that each filename mentioned in any source= of any APKBUILD
+    always has the same checksum. This is important because apk caches
+    downloaded source files in a flat distfiles directory. So if two APKBUILDs
+    both download a file with the same filename but different checksum, and the
+    user builds both after each other, abuild will fail on the second build
+    with a checksum error.
+    """
+    source_all = {}
+    for apkbuild_path in glob.iglob(f"{args.aports}/**/APKBUILD", recursive=True):
+        source = parse_source_from_checksums(args, apkbuild_path)
+        dir_path = os.path.dirname(apkbuild_path)
+        apkbuild_rel = os.path.relpath(apkbuild_path, args.aports)
+        for filename, checksum in source.items():
+            # Files bundled with the APKBUILD don't get copied to the distfiles
+            # cache, so not relevant for this check. Use glob.glob here and not
+            # iglob, because we don't want an iterator.
+            if glob.glob(f"{dir_path}/**/{filename}", recursive=True):
+                continue
+
+            # First time seeing this file
+            if filename not in source_all:
+                source_all[filename] = {"checksum": checksum,
+                                        "apkbuild_rel": apkbuild_rel}
+                continue
+
+            # Saw this file already with same checksum
+            if checksum == source_all[filename]["checksum"]:
+                continue
+
+            # Saw this file already with different checksum
+            logging.error("")
+            logging.error(f"ERROR: the source file '{filename}' has different"
+                          " checksums in the following files:")
+            logging.error(f"- {source_all[filename]['apkbuild_rel']}:")
+            logging.error(f"  {source_all[filename]['checksum']}")
+            logging.error(f"- {apkbuild_rel}:")
+            logging.error(f"  {checksum}")
+            logging.error("")
+            logging.error("Fix this by setting a different target filename in"
+                          " the package you modified:")
+            logging.error("https://wiki.alpinelinux.org/wiki/APKBUILD_Reference#source")
+            logging.error("")
+            raise RuntimeError(f"Conflict with source file '{filename}'")
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index dc55c8245..f988b05e4 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -85,18 +85,6 @@ pytest-commits:
       - pmbootstrap.cfg
     expire_in: 1 week
 
-distfile-check:
-  stage: lint
-  <<: *only-default
-  before_script:
-    - apk -q add make findutils
-    - wget "https://gitlab.com/postmarketOS/ci-common/-/archive/master/ci-common-master.tar.bz2"
-    - tar -xf ci-common-master.tar.bz2
-    - mv ci-common-master/distfile-check/*.sh ci-common-master/distfile-check/Makefile .
-    - rm -r ci-common-master ci-common-master.tar.bz2
-  script:
-    - make -j999
-
 # APKBUILD linting
 aport-lint:
   stage: lint