diff --git a/README.md b/README.md
index 833324b..cfef918 100644
--- a/README.md
+++ b/README.md
@@ -77,7 +77,9 @@ conditional
 #***************************
 # Calculate the conditional
 #***************************
-cPDF = fastkde.conditional(y, x, var_names = ['y', 'x'])
+# note that conditiong variables ('x' in this case) are listed first
+# in the var_names argument
+cPDF = fastkde.conditional(y, x, var_names = ['x', 'y'])
 ```
 
 The following plot shows the results:
diff --git a/examples/readme_test.ipynb b/examples/readme_test.ipynb
index 5309a3c..5f88921 100644
--- a/examples/readme_test.ipynb
+++ b/examples/readme_test.ipynb
@@ -215,7 +215,9 @@
     "# ***************************\n",
     "# Calculate the conditional\n",
     "# ***************************\n",
-    "cPDF = fastkde.conditional(y, x, var_names=[\"y\", \"x\"])"
+    "# note that conditiong variables ('x' in this case) are listed first\n",
+    "# in the var_names argument\n",
+    "cPDF = fastkde.conditional(y, x, var_names=[\"x\", \"y\"])"
    ]
   },
   {