diff --git a/src/gray.f b/src/gray.f
index fc7361c..8ba7b8d 100644
--- a/src/gray.f
+++ b/src/gray.f
@@ -5083,8 +5083,14 @@ c
       exom=(ffo*csgam-ui*anpl*sngam)/sqrt(deno)
       eyom=(-ffo*sngam-ui*anpl*csgam)/sqrt(deno)
 c
-      exxm=(ffx*csgam-ui*anpl*sngam)/sqrt(denx)
-      eyxm=(-ffx*sngam-ui*anpl*csgam)/sqrt(denx)
+c     if anpl=0 the expressions for exxm and eyxm are 0/0
+      if (anpl.eq.0.0_wp_) then
+        exxm=-ui*sngam
+        eyxm=-ui*csgam
+      else
+        exxm=(ffx*csgam-ui*anpl*sngam)/sqrt(denx)
+        eyxm=(-ffx*sngam-ui*anpl*csgam)/sqrt(denx)
+      end if
 c
       if (sox.lt.0.0_wp_) then
         ext=exom