diff --git a/README.md b/README.md
index bebfeb4..52bddf4 100644
--- a/README.md
+++ b/README.md
@@ -3291,7 +3291,7 @@ c  6  7
 | l.combine_first(r)     |    x   y   z  |            |            | Adds missing rows and    |
 |                        | a  1   2   .  |            |            | columns. Also updates    |
 |                        | b  3   4   5  |            |            | items that contain NaN.  |
-|                        | c  .   6   7  |            |            | R must be a DataFrame.   |
+|                        | c  .   6   7  |            |            | Argument r must be a DF. |
 +------------------------+---------------+------------+------------+--------------------------+
 ```
 
diff --git a/index.html b/index.html
index 3dbbc23..76ecdd1 100644
--- a/index.html
+++ b/index.html
@@ -2688,7 +2688,7 @@ c  <span class="hljs-number">6</span>  <span class="hljs-number">7</span>
 ┃ l.combine_first(r)     │    x   y   z  │            │            │ Adds missing rows and    ┃
 ┃                        │ a  <span class="hljs-number">1</span>   <span class="hljs-number">2</span>   .  │            │            │ columns. Also updates    ┃
 ┃                        │ b  <span class="hljs-number">3</span>   <span class="hljs-number">4</span>   <span class="hljs-number">5</span>  │            │            │ items that contain NaN.  ┃
-┃                        │ c  .   <span class="hljs-number">6</span>   <span class="hljs-number">7</span>  │            │            │ R must be a DataFrame.   ┃
+┃                        │ c  .   <span class="hljs-number">6</span>   <span class="hljs-number">7</span>  │            │            │ Argument r must be a DF. ┃
 ┗━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━━━━━━┷━━━━━━━━━━━━┷━━━━━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━┛
 </code></pre>
 <div><h4 id="dataframeaggregatetransformmap">DataFrame — Aggregate, Transform, Map:</h4><pre><code class="python language-python hljs">&lt;Sr&gt; = &lt;DF&gt;.sum/max/mean/idxmax/all()          <span class="hljs-comment"># Or: &lt;DF&gt;.apply/agg(lambda &lt;Sr&gt;: &lt;el&gt;)</span>
diff --git a/parse.js b/parse.js
index 1004e3c..ee63083 100755
--- a/parse.js
+++ b/parse.js
@@ -590,7 +590,7 @@ const DIAGRAM_15_B =
   "┃ l.combine_first(r)     │    x   y   z  │            │            │ Adds missing rows and    ┃\n" +
   "┃                        │ a  1   2   .  │            │            │ columns. Also updates    ┃\n" +
   "┃                        │ b  3   4   5  │            │            │ items that contain NaN.  ┃\n" +
-  "┃                        │ c  .   6   7  │            │            │ R must be a DataFrame.   ┃\n" +
+  "┃                        │ c  .   6   7  │            │            │ Argument r must be a DF. ┃\n" +
   "┗━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━━━━━━┷━━━━━━━━━━━━┷━━━━━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━┛\n";
 
 const DIAGRAM_16_A =