diff --git a/src/interpolate.cpp b/src/interpolate.cpp
index 3693b4e..d9e3e4f 100644
--- a/src/interpolate.cpp
+++ b/src/interpolate.cpp
@@ -107,7 +107,10 @@ const Interpolate& Interpolate::operator=(const Interpolate& a)
 
 double Interpolate::getMaxX() const
 {
-  return exp(spline->x[spline->size-1]);
+  if (logx)
+    return exp(spline->x[spline->size-1]);
+  else
+    return spline->x[spline->size-1];
 }
 
 typedef struct {