diff --git a/guix/build-system/perl.scm b/guix/build-system/perl.scm
index 0d5493ab90..3f7a2dea27 100644
--- a/guix/build-system/perl.scm
+++ b/guix/build-system/perl.scm
@@ -197,7 +197,9 @@ XS or similar."
                                native-search-paths))
                       #:make-maker? #$make-maker?
                       #:make-maker-flags #$make-maker-flags
-                      #:module-build-flags #$(sexp->gexp module-build-flags)
+                      #:module-build-flags #$(if (pair? module-build-flags)
+                                                 (sexp->gexp module-build-flags)
+                                                 module-build-flags)
                       #:phases #$phases
                       #:build #$build
                       #:system #$system