diff --git a/src/Posting/Captcha.replace.coffee b/src/Posting/Captcha.replace.coffee
index a58864dde..42324e2a9 100644
--- a/src/Posting/Captcha.replace.coffee
+++ b/src/Posting/Captcha.replace.coffee
@@ -8,9 +8,9 @@ Captcha.replace =
 
     if Conf['captchaLanguage'].trim() or Conf['Captcha Fixes']
       if location.hostname in ['boards.4chan.org', 'boards.4channel.org']
-        $.onExists doc, '#captchaFormPart', (node) -> $.onExists node, 'iframe', Captcha.replace.iframe
+        $.onExists doc, '#captchaFormPart', (node) -> $.onExists node, 'iframe[src^="https://www.google.com/recaptcha/"]', Captcha.replace.iframe
       else
-        $.onExists doc, 'iframe', Captcha.replace.iframe
+        $.onExists doc, 'iframe[src^="https://www.google.com/recaptcha/"]', Captcha.replace.iframe
 
   noscript: ->
     return if not ((original = $ '#g-recaptcha') and (noscript = $ 'noscript', original.parentNode))
@@ -20,7 +20,7 @@ Captcha.replace =
     $.rm original
     insert = ->
       span.innerHTML = noscript.textContent
-      Captcha.replace.iframe $('iframe', span)
+      Captcha.replace.iframe $('iframe[src^="https://www.google.com/recaptcha/"]', span)
     if (toggle = $ '#togglePostFormLink a, #form-link')
       $.on toggle, 'click', insert
     else
diff --git a/src/Posting/Captcha.v2.coffee b/src/Posting/Captcha.v2.coffee
index 41fcf41f4..de27a3d53 100644
--- a/src/Posting/Captcha.v2.coffee
+++ b/src/Posting/Captcha.v2.coffee
@@ -69,7 +69,7 @@ Captcha.v2 =
     if @nodes.container
       # XXX https://bugzilla.mozilla.org/show_bug.cgi?id=1226835
       $.queueTask =>
-        if @nodes.container and d.activeElement is @nodes.counter and (iframe = $ 'iframe', @nodes.container)
+        if @nodes.container and d.activeElement is @nodes.counter and (iframe = $ 'iframe[src^="https://www.google.com/recaptcha/"]', @nodes.container)
           iframe.focus()
           QR.focus() # Event handler not fired in Firefox
       return
@@ -120,7 +120,7 @@ Captcha.v2 =
   afterSetup: (mutations) ->
     for mutation in mutations
       for node in mutation.addedNodes
-        @setupIFrame   iframe   if (iframe   = $.x './descendant-or-self::iframe',   node)
+        @setupIFrame   iframe   if (iframe   = $.x './descendant-or-self::iframe[starts-with(@src, "https://www.google.com/recaptcha/")]',   node)
         @setupTextArea textarea if (textarea = $.x './descendant-or-self::textarea', node)
     return