diff --git a/server/modules/rendering/markdown-kroki/renderer.js b/server/modules/rendering/markdown-kroki/renderer.js
index 1487f737..801bab6d 100644
--- a/server/modules/rendering/markdown-kroki/renderer.js
+++ b/server/modules/rendering/markdown-kroki/renderer.js
@@ -73,8 +73,13 @@ module.exports = {
             continue
           }
 
-          const i = closeMarker.findIndex(item => item !== state.src[start + i])
-          const closeMarkerMatched = i !== -1
+          let closeMarkerMatched = true
+          for (i = 0; i < closeMarker.length; ++i) {
+            if (closeMarker[i] !== state.src[start + i]) {
+              closeMarkerMatched = false
+              break
+            }
+          }
 
           if (!closeMarkerMatched) {
             continue
diff --git a/server/modules/rendering/markdown-plantuml/renderer.js b/server/modules/rendering/markdown-plantuml/renderer.js
index 0ad67e9e..40eedc04 100644
--- a/server/modules/rendering/markdown-plantuml/renderer.js
+++ b/server/modules/rendering/markdown-plantuml/renderer.js
@@ -74,8 +74,13 @@ module.exports = {
             continue
           }
 
-          const i = closeMarker.findIndex(item => item !== state.src[start + i])
-          const closeMarkerMatched = i !== -1
+          let closeMarkerMatched = true
+          for (i = 0; i < closeMarker.length; ++i) {
+            if (closeMarker[i] !== state.src[start + i]) {
+              closeMarkerMatched = false
+              break
+            }
+          }
 
           if (!closeMarkerMatched) {
             continue