diff --git a/envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.proto b/envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.proto
index 0ef96f17..3b56da81 100644
--- a/envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.proto
+++ b/envoy/config/filter/http/header_to_metadata/v2/header_to_metadata.proto
@@ -69,7 +69,8 @@ message Config {
   // A Rule defines what metadata to apply when a header is present or missing.
   message Rule {
     // The header that triggers this rule — required.
-    string header = 1 [(validate.rules).string = {min_bytes: 1}];
+    string header = 1
+        [(validate.rules).string = {min_bytes: 1 well_known_regex: HTTP_HEADER_NAME strict: false}];
 
     // If the header is present, apply this metadata KeyValuePair.
     //
diff --git a/envoy/extensions/filters/http/header_to_metadata/v3/header_to_metadata.proto b/envoy/extensions/filters/http/header_to_metadata/v3/header_to_metadata.proto
index 249c6129..59fe59c1 100644
--- a/envoy/extensions/filters/http/header_to_metadata/v3/header_to_metadata.proto
+++ b/envoy/extensions/filters/http/header_to_metadata/v3/header_to_metadata.proto
@@ -77,7 +77,8 @@ message Config {
         "envoy.config.filter.http.header_to_metadata.v2.Config.Rule";
 
     // The header that triggers this rule — required.
-    string header = 1 [(validate.rules).string = {min_bytes: 1}];
+    string header = 1
+        [(validate.rules).string = {min_bytes: 1 well_known_regex: HTTP_HEADER_NAME strict: false}];
 
     // If the header is present, apply this metadata KeyValuePair.
     //