diff --git a/interpolation/akima.c b/interpolation/akima.c
index 551bb8b..4244e0f 100644
--- a/interpolation/akima.c
+++ b/interpolation/akima.c
@@ -350,7 +350,7 @@ akima_eval_integ (const void * vstate,
     }
     else {
       *result = 0.0;
-      return GSL_FAILURE;
+      return GSL_EINVAL;
     }
   }