diff --git a/db/migrate/20230103004613_make_experimental_hashtag_feature_default_for_new_sites.rb b/db/migrate/20230103004613_make_experimental_hashtag_feature_default_for_new_sites.rb
index e0047fdb3c4..55f6d340367 100644
--- a/db/migrate/20230103004613_make_experimental_hashtag_feature_default_for_new_sites.rb
+++ b/db/migrate/20230103004613_make_experimental_hashtag_feature_default_for_new_sites.rb
@@ -2,11 +2,21 @@
 
 class MakeExperimentalHashtagFeatureDefaultForNewSites < ActiveRecord::Migration[7.0]
   def up
-    execute(<<~SQL)
+    result = execute <<~SQL
+      SELECT created_at
+      FROM schema_migration_details
+      ORDER BY created_at
+      LIMIT 1
+    SQL
+
+    settings_insert_query = <<~SQL
       INSERT INTO site_settings (name, data_type, value, created_at, updated_at)
       VALUES ('enable_experimental_hashtag_autocomplete', 5, 'f', now(), now())
       ON CONFLICT DO NOTHING
     SQL
+
+    # keep enable_experimental_hashtag_autocomplete disabled for for existing sites
+    execute settings_insert_query if result.first["created_at"].to_datetime < 1.hour.ago
   end
 
   def down
diff --git a/plugins/chat/spec/models/chat_message_spec.rb b/plugins/chat/spec/models/chat_message_spec.rb
index 1ce6a39ed36..9e305f98f25 100644
--- a/plugins/chat/spec/models/chat_message_spec.rb
+++ b/plugins/chat/spec/models/chat_message_spec.rb
@@ -234,8 +234,10 @@ describe ChatMessage do
       expect(cooked).to eq("<p><span class=\"mention\">@mention</span></p>")
     end
 
-    # TODO (martin) Remove this when enable_experimental_hashtag_autocomplete is default
     it "supports category-hashtag plugin" do
+      # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+      SiteSetting.enable_experimental_hashtag_autocomplete = false
+
       category = Fabricate(:category)
 
       cooked = ChatMessage.cook("##{category.slug}")
diff --git a/plugins/discourse-narrative-bot/spec/discourse_narrative_bot/advanced_user_narrative_spec.rb b/plugins/discourse-narrative-bot/spec/discourse_narrative_bot/advanced_user_narrative_spec.rb
index 82e5024e99e..14561dceed8 100644
--- a/plugins/discourse-narrative-bot/spec/discourse_narrative_bot/advanced_user_narrative_spec.rb
+++ b/plugins/discourse-narrative-bot/spec/discourse_narrative_bot/advanced_user_narrative_spec.rb
@@ -494,6 +494,9 @@ RSpec.describe DiscourseNarrativeBot::AdvancedUserNarrative do
       end
 
       it "should create the right reply" do
+        # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+        SiteSetting.enable_experimental_hashtag_autocomplete = false
+
         category = Fabricate(:category)
 
         post.update!(raw: "Check out this ##{category.slug}")
diff --git a/spec/integrity/common_mark_spec.rb b/spec/integrity/common_mark_spec.rb
index c89f9ff0e81..85c8c821227 100644
--- a/spec/integrity/common_mark_spec.rb
+++ b/spec/integrity/common_mark_spec.rb
@@ -5,6 +5,9 @@ RSpec.describe "CommonMark" do
     SiteSetting.enable_markdown_typographer = false
     SiteSetting.highlighted_languages = "ruby|aa"
 
+    # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+    SiteSetting.enable_experimental_hashtag_autocomplete = false
+
     html, state, md = nil
     failed = 0
 
diff --git a/spec/lib/pretty_text_spec.rb b/spec/lib/pretty_text_spec.rb
index 25a8d80749b..7b3ef983203 100644
--- a/spec/lib/pretty_text_spec.rb
+++ b/spec/lib/pretty_text_spec.rb
@@ -1619,6 +1619,9 @@ RSpec.describe PrettyText do
   end
 
   it "produces hashtag links" do
+    # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+    SiteSetting.enable_experimental_hashtag_autocomplete = false
+
     category = Fabricate(:category, name: "testing")
     category2 = Fabricate(:category, name: "known")
     Fabricate(:topic, tags: [Fabricate(:tag, name: "known")])
@@ -1908,6 +1911,9 @@ HTML
     end
 
     it "does not replace hashtags and mentions" do
+      # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+      SiteSetting.enable_experimental_hashtag_autocomplete = false
+
       Fabricate(:user, username: "test")
       category = Fabricate(:category, slug: "test")
       Fabricate(
@@ -1927,6 +1933,9 @@ HTML
     end
 
     it "does not replace hashtags and mentions when watched words are regular expressions" do
+      # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+      SiteSetting.enable_experimental_hashtag_autocomplete = false
+
       SiteSetting.watched_words_regular_expressions = true
 
       Fabricate(:user, username: "test")
diff --git a/spec/requests/hashtags_controller_spec.rb b/spec/requests/hashtags_controller_spec.rb
index 9cffbf5b96f..2d2b0f3ca67 100644
--- a/spec/requests/hashtags_controller_spec.rb
+++ b/spec/requests/hashtags_controller_spec.rb
@@ -14,6 +14,10 @@ RSpec.describe HashtagsController do
 
   before do
     SiteSetting.tagging_enabled = true
+
+    # TODO (martin) Remove when enable_experimental_hashtag_autocomplete is default for all sites
+    SiteSetting.enable_experimental_hashtag_autocomplete = false
+
     tag_group
   end