diff --git a/lib/discourse_activity_pub/json_ld.rb b/lib/discourse_activity_pub/json_ld.rb
index d4dea7a7..e326e6e0 100644
--- a/lib/discourse_activity_pub/json_ld.rb
+++ b/lib/discourse_activity_pub/json_ld.rb
@@ -75,6 +75,7 @@ def valid_content_type?(value)
     end
 
     def valid_accept?(value)
+      return false if value.blank?
       value.split(",").compact.collect(&:strip).all? { |v| valid_content_type?(v) }
     end
 
diff --git a/spec/lib/discourse_activity_pub/json_ld_spec.rb b/spec/lib/discourse_activity_pub/json_ld_spec.rb
index 8d5a39f7..99f1e50e 100644
--- a/spec/lib/discourse_activity_pub/json_ld_spec.rb
+++ b/spec/lib/discourse_activity_pub/json_ld_spec.rb
@@ -45,6 +45,10 @@
         false,
       )
     end
+
+    it "does not validate empty accept headers" do
+      expect(described_class.valid_accept?(nil)).to eq(false)
+    end
   end
 
   describe "#address_json" do