diff --git a/rtengine/LUT.h b/rtengine/LUT.h
index b58144a6f..29147df8b 100644
--- a/rtengine/LUT.h
+++ b/rtengine/LUT.h
@@ -200,6 +200,10 @@ public:
         clip = flags;
     }
 
+    int getClip() const {
+        return clip;
+    }
+
     /** @brief Get the number of element in the LUT (i.e. dimension of the array)
      *  For a LUT(500), it will return 500
      *  @return number of element in the array
@@ -304,6 +308,9 @@ public:
     }
 
 #if defined( __SSE2__ ) && defined( __x86_64__ )
+
+    // NOTE: This version requires LUTs which clip at upper and lower bounds
+    // (which is the default).
     vfloat operator[](vfloat indexv) const
     {
         static_assert(std::is_same<T, float>::value, "This method only works for float LUTs");
diff --git a/rtengine/curves.h b/rtengine/curves.h
index 15ab96624..e8b65c33d 100644
--- a/rtengine/curves.h
+++ b/rtengine/curves.h
@@ -886,6 +886,8 @@ inline void StandardToneCurve::BatchApply(
         const size_t start, const size_t end,
         float *r, float *g, float *b) const {
     assert (lutToneCurve);
+    assert (lutToneCurve.getClip() & LUT_CLIP_BELOW);
+    assert (lutToneCurve.getClip() & LUT_CLIP_ABOVE);
 
     // All pointers must have the same alignment for SSE usage. In the loop body below,
     // we will only check `r`, assuming that the same result would hold for `g` and `b`.