diff --git a/app/models/agents/post_agent.rb b/app/models/agents/post_agent.rb
index 5f13bd48d5..7182107a3f 100644
--- a/app/models/agents/post_agent.rb
+++ b/app/models/agents/post_agent.rb
@@ -144,7 +144,7 @@ def validate_options
         errors.add(:base, "if provided, output_mode must be 'clean' or 'merge'")
       end
 
-      if options['parse_body'].present? && /\A(?:true|false)\z|\{/.match?(options['parse_body'].to_s)
+      if options['parse_body'].present? && !/\A(?:true|false)\z|\{/.match?(options['parse_body'].to_s)
         errors.add(:base, "if provided, parse_body must be 'true' or 'false'")
       end
 
diff --git a/spec/models/agents/post_agent_spec.rb b/spec/models/agents/post_agent_spec.rb
index e98b9702ef..40951e09cf 100644
--- a/spec/models/agents/post_agent_spec.rb
+++ b/spec/models/agents/post_agent_spec.rb
@@ -303,6 +303,7 @@
 
           it "emits the parsed JSON body when parse_body is true" do
             @checker.options['parse_body'] = 'true'
+            @checker.save!
             @checker.check
             expect(@checker.events.last.payload['body']).to eq json_data
           end