diff --git a/src/gray.f b/src/gray.f
index 46505e2..3d48d4a 100644
--- a/src/gray.f
+++ b/src/gray.f
@@ -933,7 +933,7 @@ c
 c     print resonant B iequil=1
 c
       write(70,*)'#i Btot  R  z'
-      rres=bres*rr0m/b0
+      rres=b0*rr0m/bres
       zmx=zr0m+rpam
       zmn=zr0m-rpam
       do i=1,21