diff --git a/module_build_service/utils/reuse.py b/module_build_service/utils/reuse.py
index efbbc0a..d548264 100644
--- a/module_build_service/utils/reuse.py
+++ b/module_build_service/utils/reuse.py
@@ -25,7 +25,7 @@
import kobo.rpmlib
import module_build_service.messaging
-from module_build_service import log, models, conf
+from module_build_service import log, models, conf, glib
def reuse_component(component, previous_component_build,
@@ -110,6 +110,21 @@ def _get_reusable_module(session, module):
log.info("Cannot re-use. %r is the first module build." % module)
return None
+ xmd = glib.from_variant_dict(mmd.get_xmd())
+ old_mmd = previous_module_build.mmd()
+ old_xmd = glib.from_variant_dict(old_mmd.get_xmd())
+
+ # Make sure that the module buildrequires commit hashes are exactly the same
+ for br_module_name, br_module in xmd['mbs']['buildrequires'].items():
+ # Assumes that the streams have been replaced with commit hashes, so we
+ # can compare to see if they have changed. Since a build is unique to
+ # a commit hash, this is a safe test.
+ ref1 = br_module.get('ref')
+ ref2 = old_xmd['mbs']['buildrequires'][br_module_name].get('ref')
+ if not (ref1 and ref2) or ref1 != ref2:
+ log.info('Cannot re-use. The buildrequired module %s ref hash changed', br_module_name)
+ return None
+
return previous_module_build