diff --git a/pyqtgraph/functions_numba.py b/pyqtgraph/functions_numba.py
index 83fdb8b1..3df568fb 100644
--- a/pyqtgraph/functions_numba.py
+++ b/pyqtgraph/functions_numba.py
@@ -22,19 +22,19 @@ def rescaleData(data, scale, offset, dtype, clip):
     return data_out
 
 @numba.jit(nopython=True)
-def rescale_and_lookup1d_function(xx, scale, offset, lut, yy):
+def _rescale_and_lookup1d_function(data, scale, offset, lut, out):
     vmin, vmax = 0, lut.shape[0] - 1
-    for r in range(xx.shape[0]):
-        for c in range(xx.shape[1]):
-            val = (xx[r, c] - offset) * scale
+    for r in range(data.shape[0]):
+        for c in range(data.shape[1]):
+            val = (data[r, c] - offset) * scale
             val = min(max(val, vmin), vmax)
-            yy[r, c] = lut[int(val)]
+            out[r, c] = lut[int(val)]
 
 def rescale_and_lookup1d(data, scale, offset, lut):
     # data should be floating point and 2d
     # lut is 1d
     data_out = np.empty_like(data, dtype=lut.dtype)
-    rescale_and_lookup1d_function(data, float(scale), float(offset), lut, data_out)
+    _rescale_and_lookup1d_function(data, float(scale), float(offset), lut, data_out)
     return data_out
 
 @numba.jit(nopython=True)