diff --git a/README.md b/README.md
index 26e46fc..3cd379e 100644
--- a/README.md
+++ b/README.md
@@ -3209,8 +3209,8 @@ c  6  7
 +------------------------+---------------+------------+------------+--------------------------+
 | l.join(r, lsuffix='l', |    x yl yr  z |            | x yl yr  z | Joins/merges on row keys.|
 |           rsuffix='r', | a  1  2  .  . | x yl yr  z | 1  2  .  . | Uses 'left' by default.  |
-|           how=…)       | b  3  4  4  5 | 3  4  4  5 | 3  4  4  5 |                          |
-|                        | c  .  .  6  7 |            |            |                          |
+|           how=…)       | b  3  4  4  5 | 3  4  4  5 | 3  4  4  5 | If 'r' is a series, it   |
+|                        | c  .  .  6  7 |            |            | is first converted to DF.|
 +------------------------+---------------+------------+------------+--------------------------+
 | pd.concat([l, r],      |    x   y   z  |     y      |            | Adds rows at the bottom. |
 |           axis=0,      | a  1   2   .  |     2      |            | Uses 'outer' by default. |
diff --git a/index.html b/index.html
index fe355f0..24e77a1 100644
--- a/index.html
+++ b/index.html
@@ -2733,8 +2733,8 @@ c  <span class="hljs-number">6</span>  <span class="hljs-number">7</span>
 ┠────────────────────────┼───────────────┼────────────┼────────────┼──────────────────────────┨
 ┃ l.join(r, lsuffix=<span class="hljs-string">'l'</span>, │    x yl yr  z │            │ x yl yr  z │ Joins/merges on row keys.┃
 ┃           rsuffix=<span class="hljs-string">'r'</span>, │ a  <span class="hljs-number">1</span>  <span class="hljs-number">2</span>  .  . │ x yl yr  z │ <span class="hljs-number">1</span>  <span class="hljs-number">2</span>  .  . │ Uses <span class="hljs-string">'left'</span> by default.  ┃
-┃           how=…)       │ b  <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │ <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │ <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │                          ┃
-┃                        │ c  .  .  <span class="hljs-number">6</span>  <span class="hljs-number">7</span> │            │            │                          ┃
+┃           how=…)       │ b  <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │ <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │ <span class="hljs-number">3</span>  <span class="hljs-number">4</span>  <span class="hljs-number">4</span>  <span class="hljs-number">5</span> │ If <span class="hljs-string">'r'</span> is a series, it   ┃
+┃                        │ c  .  .  <span class="hljs-number">6</span>  <span class="hljs-number">7</span> │            │            │ is first converted to DF.┃
 ┠────────────────────────┼───────────────┼────────────┼────────────┼──────────────────────────┨
 ┃ pd.concat([l, r],      │    x   y   z  │     y      │            │ Adds rows at the bottom. ┃
 ┃           axis=<span class="hljs-number">0</span>,      │ a  <span class="hljs-number">1</span>   <span class="hljs-number">2</span>   .  │     <span class="hljs-number">2</span>      │            │ Uses <span class="hljs-string">'outer'</span> by default. ┃
diff --git a/parse.js b/parse.js
index bac2cee..4fc160e 100755
--- a/parse.js
+++ b/parse.js
@@ -320,8 +320,8 @@ const DIAGRAM_15_B =
   "┠────────────────────────┼───────────────┼────────────┼────────────┼──────────────────────────┨\n" +
   "┃ l.join(r, lsuffix='l', │    x yl yr  z │            │ x yl yr  z │ Joins/merges on row keys.┃\n" +
   "┃           rsuffix='r', │ a  1  2  .  . │ x yl yr  z │ 1  2  .  . │ Uses 'left' by default.  ┃\n" +
-  "┃           how=…)       │ b  3  4  4  5 │ 3  4  4  5 │ 3  4  4  5 │                          ┃\n" +
-  "┃                        │ c  .  .  6  7 │            │            │                          ┃\n" +
+  "┃           how=…)       │ b  3  4  4  5 │ 3  4  4  5 │ 3  4  4  5 │ If 'r' is a series, it   ┃\n" +
+  "┃                        │ c  .  .  6  7 │            │            │ is first converted to DF.┃\n" +
   "┠────────────────────────┼───────────────┼────────────┼────────────┼──────────────────────────┨\n" +
   "┃ pd.concat([l, r],      │    x   y   z  │     y      │            │ Adds rows at the bottom. ┃\n" +
   "┃           axis=0,      │ a  1   2   .  │     2      │            │ Uses 'outer' by default. ┃\n" +
@@ -549,6 +549,7 @@ function fixPandasDiagram() {
   const diagram_15 = '┏━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━━━━━━━┯━━━━━━━━━━━━┯━━━━━━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━┓';
   $(`code:contains(${diagram_15})`).find(".hljs-keyword:contains(and)").after("and");
   $(`code:contains(${diagram_15})`).find(".hljs-keyword:contains(as)").after("as");
+  $(`code:contains(${diagram_15})`).find(".hljs-keyword:contains(is)").after("is");
   $(`code:contains(${diagram_15})`).find(".hljs-keyword").remove();
 }