diff --git a/guix/build/python-build-system.scm b/guix/build/python-build-system.scm
index 9109fb4..65824a3 100644
--- a/guix/build/python-build-system.scm
+++ b/guix/build/python-build-system.scm
@@ -44,9 +44,9 @@
          (zero? (apply system* "python" "setup.py" command params)))
       (error "no setup.py found")))
 
-(define* (build #:rest empty)
+(define* (build #:key (configure-flags '()) #:allow-other-keys)
   "Build a given Python package."
-  (call-setuppy "build" '()))
+  (call-setuppy "build" configure-flags))
 
 (define* (check #:key tests? test-target #:allow-other-keys)
   "Run the test suite of a given Python package."