diff --git a/doc/guide/dhcp4-srv.xml b/doc/guide/dhcp4-srv.xml
index 6c74a2fada..f21ee4b2e2 100644
--- a/doc/guide/dhcp4-srv.xml
+++ b/doc/guide/dhcp4-srv.xml
@@ -1016,6 +1016,34 @@ temporarily override a list of interface names and listen on all interfaces.
         structures. "Type" designates the format of the data: the meanings of
         the various types is given in <xref linkend="dhcp-types"/>.
       </para>
+
+      <para>When the data field is a string, and that string contains the comma
+      (,; U+002C) character, the comma must be escaped with a reverse solidus
+      character (\; U+005C). For example, the string
+      &quot;foo,bar&quot; would be represented as:
+      <screen>
+"Dhcp4": {
+    "subnet4": [
+        {
+            "pools": [
+                {
+                    <userinput>"option-data": [
+                        {
+                            "name": "boot-file-name",
+                            "data": "foo\,bar"
+                        }
+                    ]</userinput>
+                },
+                ...
+            ],
+            ...
+        },
+        ...
+    ],
+    ...
+}
+</screen>
+      </para>
       <para>
         Some options are designated as arrays, which means that more than one
         value is allowed in such an option. For example the option time-servers
diff --git a/doc/guide/dhcp6-srv.xml b/doc/guide/dhcp6-srv.xml
index 166c932e66..89a731767c 100644
--- a/doc/guide/dhcp6-srv.xml
+++ b/doc/guide/dhcp6-srv.xml
@@ -1050,6 +1050,33 @@ temporarily override a list of interface names and listen on all interfaces.
       which was not assigned by IANA) are listed in
       <xref linkend="dhcp6-exp-options-list"/>.
     </para>
+    <para>When the data field is a string, and that string contains the comma
+    (,; U+002C) character, the comma must be escaped with a reverse solidus
+    character (\; U+005C). For example, the string &quot;EST5EDT4,M3.2.0/02:00,M11.1.0/02:00&quot; would be
+    represented as:
+<screen>
+"Dhcp6": {
+    "subnet6": [
+        {
+            "pools": [
+                {
+                    <userinput>"option-data": [
+                        {
+                            "name": "new-posix-timezone",
+                            "data": "EST5EDT4\,M3.2.0/02:00\,M11.1.0/02:00"
+                        }
+                    ]</userinput>
+                },
+                ...
+            ],
+            ...
+        },
+        ...
+    ],
+    ...
+}
+</screen>
+    </para>
     <para>
       Some options are designated as arrays, which means that more than one
       value is allowed in such an option. For example the option dns-servers