diff --git a/math/Makefile b/math/Makefile
index 46a005483a04..e7de3dd74a4d 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -678,6 +678,7 @@
     SUBDIR += rapid
     SUBDIR += reduce
     SUBDIR += reed-solomon
+    SUBDIR += rexx-regmath
     SUBDIR += rkward-kde4
     SUBDIR += rngstreams
     SUBDIR += rocs