diff --git a/spack-environment/Makefile b/spack-environment/Makefile
index 3e2d12d7d40b02f1cc7138fd8f4bb664d933c4d6..01e9bf95d394727a294e1640f90716154658904c 100644
--- a/spack-environment/Makefile
+++ b/spack-environment/Makefile
@@ -22,15 +22,15 @@ include $(SPACK_ENV)/spack.mk
 endif
 
 $(SPACK_ENV)/push: $(addprefix $(SPACK_ENV)/push/,$($(SPACK_ENV)/SPACK_PACKAGE_IDS))
-	$(foreach buildcache, $(BUILDCACHE_S3_FINAL), $(SPACK) buildcache push --unsigned $(buildcache) ;)
+	$(foreach buildcache, $(BUILDCACHE_S3_FINAL), $(SPACK) buildcache push --private --unsigned $(buildcache) ;)
 	$(foreach buildcache, $(BUILDCACHE_S3_FINAL), $(SPACK) buildcache update-index $(buildcache) ;)
 	$(foreach buildcache, $(BUILDCACHE_S3_PROMPT), $(SPACK) buildcache update-index $(buildcache) ;)
-	$(foreach buildcache, $(BUILDCACHE_OCI_FINAL), $(SPACK) buildcache push --force --unsigned --base-image $(BUILDCACHE_OCI_BASE_IMAGE) $(buildcache) | grep -v "Using cached archive" ;)
+	$(foreach buildcache, $(BUILDCACHE_OCI_FINAL), $(SPACK) buildcache push --private --force --unsigned --base-image $(BUILDCACHE_OCI_BASE_IMAGE) $(buildcache) | grep -v "Using cached archive" ;)
 
 $(SPACK_ENV)/push/%: $(SPACK_ENV)/install/%
 	@mkdir -p $(dir $@)
-	$(foreach buildcache, $(BUILDCACHE_S3_PROMPT), $(SPACK) buildcache push --unsigned --only=package $(buildcache) /$(HASH) ;) # push $(SPEC)
-	$(foreach buildcache, $(BUILDCACHE_OCI_PROMPT), $(SPACK) buildcache push --unsigned --base-image $(BUILDCACHE_OCI_BASE_IMAGE) $(buildcache) /$(HASH) | grep -v "Using cached archive" ;) # push $(SPEC)
+	$(foreach buildcache, $(BUILDCACHE_S3_PROMPT), $(SPACK) buildcache push --private --unsigned --only=package $(buildcache) /$(HASH) ;) # push $(SPEC)
+	$(foreach buildcache, $(BUILDCACHE_OCI_PROMPT), $(SPACK) buildcache push --private --unsigned --base-image $(BUILDCACHE_OCI_BASE_IMAGE) $(buildcache) /$(HASH) | grep -v "Using cached archive" ;) # push $(SPEC)
 	@touch $@
 
 $(SPACK_ENV)/spack.lock: $(SPACK_ENV)/spack.yaml Makefile