diff --git a/APKBUILD b/APKBUILD
index 42e72ac6105628909c490cb9cd60abb9912f4e43..ba12ce9cd5acdb3bc762008bc5f9fc44b170d0d4 100644
--- a/APKBUILD
+++ b/APKBUILD
@@ -33,7 +33,10 @@ 	# stylesheet built afterwards would never make it into the binary. The
 	# shared scss partials are assembled by CI at ASSETS/scss (no apk ships
 	# them).
 	make css ASSETS=/usr/share/sourcehut
-	CGO_ENABLED=0 make build GOFLAGS="-trimpath"
+	# -modcacherw matters beyond convenience: without it the module cache is
+	# extracted read-only, and the CI cache tarball made from it can't be
+	# unpacked on the next build (mkdir into 0555 dirs fails).
+	CGO_ENABLED=0 make build GOFLAGS="-trimpath -modcacherw"
 }
 
 package() {