diff --git a/cssom-1/Overview.bs b/cssom-1/Overview.bs
index f0fee38dc505..1a266b26d79a 100644
--- a/cssom-1/Overview.bs
+++ b/cssom-1/Overview.bs
@@ -1523,17 +1523,34 @@ To serialize a CSS rule, perform one of the following in accor
- {{CSSStyleRule}}
-
- The result of concatenating the following:
+ Return the result of the following steps:
+
- - The result of performing serialize a group of selectors on the rule's associated selectors.
-
- The string "
{ ", i.e., a single SPACE (U+0020), followed by LEFT CURLY BRACKET (U+007B),
- followed by a single SPACE (U+0020).
- - The result of performing serialize a CSS declaration block on the rule's associated declarations.
-
- If the rule is associated with one or more declarations, the string "
", i.e., a single SPACE (U+0020).
- - The string "
}", RIGHT CURLY BRACKET (U+007D).
+ - Let |s| initially be
+ the result of performing serialize a group of selectors on the rule's associated selectors,
+ followed by the string "
{", i.e., a single SPACE (U+0020), followed by LEFT CURLY BRACKET (U+007B).
+ - Let |decls| be the result of performing serialize a CSS declaration block on the rule's associated declarations, or null if there are no such declarations.
+
- Let |rules| be the result of performing [=serialize a CSS rule=] on each rule in the rule's {{CSSStyleRule/cssRules}} list, or null if there are no such rules.
+
- If |decls| and |rules| are both null, append " }" to |s| (i.e. a single SPACE (U+0020) followed by RIGHT CURLY BRACKET (U+007D)) and return |s|.
+
- If |rules| is null:
+
+ - Append a single SPACE (U+0020) to |s|
+
- Append |decls| to |s|
+
- Append " }" to |s| (i.e. a single SPACE (U+0020) followed by RIGHT CURLY BRACKET (U+007D)).
+
- Return |s|.
+
+ - Otherwise:
+
+ - If |decls| is not null, prepend it to |rules|.
+
- For each |rule| in |rules|:
+
+ - Append a newline followed by two spaces to |s|.
+
- Append |rule| to |s|.
+
+ - Append a newline followed by RIGHT CURLY BRACKET (U+007D) to |s|.
+
- Return |s|.
-
- {{CSSImportRule}}
-
The result of concatenating the following: