diff --git a/rulesets/src/request-response.ruleset.yml b/rulesets/src/request-response.ruleset.yml
index afe86ff..25bbddf 100644
--- a/rulesets/src/request-response.ruleset.yml
+++ b/rulesets/src/request-response.ruleset.yml
@@ -115,7 +115,7 @@ rules:
         notMatch: "^(Access-Control-.*|Content-Type|Accept)$"
 
   sps-invalid-custom-header-format:
-    description: Custom headers MUST NOT be longer than 50 chars, and MUST only contain alphanumeric and dash chars, and MUST begin with SPS- not x-
+    description: Custom headers MUST NOT be longer than 50 chars, and MUST only contain alphanumeric and dash chars, and MUST begin with Sps- not X-
     severity: error
     given: "$.paths[*][*].responses[*].headers.*~"
     then: