diff --git a/x-pack/legacy/plugins/siem/public/containers/detection_engine/rules/api.ts b/x-pack/legacy/plugins/siem/public/containers/detection_engine/rules/api.ts
index 4f50a9bd14788..06fb0c6dc3480 100644
--- a/x-pack/legacy/plugins/siem/public/containers/detection_engine/rules/api.ts
+++ b/x-pack/legacy/plugins/siem/public/containers/detection_engine/rules/api.ts
@@ -246,6 +246,7 @@ export const importRules = async ({
     `${DETECTION_ENGINE_RULES_URL}/_import`,
     {
       method: 'POST',
+      headers: { 'Content-Type': undefined },
       query: { overwrite },
       body: formData,
       asResponse: true,