diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index df903a4b4d..72ec7db3d7 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -9309,6 +9309,19 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-SDK_SYS'><glossterm><imagedata fileref="figures/define-generic.png" />SDK_SYS</glossterm>
+            <info>
+                SDK_SYS[doc] = "Specifies the SDK system, including the architecture and the operating system, for which the build is occurring in the context of the current recipe."
+            </info>
+            <glossdef>
+                <para>
+                    Specifies the SDK system, including the architecture and
+                    the operating system, for which the build is occurring
+                    in the context of the current recipe.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-SDKIMAGE_FEATURES'><glossterm><imagedata fileref="figures/define-generic.png" />SDKIMAGE_FEATURES</glossterm>
             <info>
                 SDKIMAGE_FEATURES[doc] = "Equivalent to IMAGE_FEATURES. However, this variable applies to the SDK generated from an image using the command 'bitbake -c populate_sdk imagename'."