diff --git a/.gitmodules b/.gitmodules
index 51dcbfae092e4..f1853e37a2e27 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -192,3 +192,7 @@
 	path = extensions/UniversalLanguageSelector
 	url = https://github.com/wikimedia/mediawiki-extensions-UniversalLanguageSelector.git
 	branch = REL1_39
+[submodule "extensions/CodeMirror"]
+	path = extensions/CodeMirror
+	url = https://github.com/wikimedia/mediawiki-extensions-CodeMirror.git
+	branch = REL1_39
diff --git a/extensions/CodeMirror b/extensions/CodeMirror
new file mode 160000
index 0000000000000..78dea4ba8ed2b
--- /dev/null
+++ b/extensions/CodeMirror
@@ -0,0 +1 @@
+Subproject commit 78dea4ba8ed2b082cd35498c341dfa5d33ad75f3