diff --git a/OpenCloudSDK/Bookmark/OCBookmark.h b/OpenCloudSDK/Bookmark/OCBookmark.h
index 0b40b896..7d002157 100644
--- a/OpenCloudSDK/Bookmark/OCBookmark.h
+++ b/OpenCloudSDK/Bookmark/OCBookmark.h
@@ -101,6 +101,8 @@ extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyStatusInfo; //!<  .userInfo ke
 extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyAllowHTTPConnection; //!< .userInfo key with a NSDate value. To be set to the date that the user was informed and allowed the usage of HTTP. To be removed otherwise.
 extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyBookmarkCreation; //!<  .userInfo key with a NSDictionary holding information on the creation of the bookmark.
 extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyPreferredUsername; //!< .userInfo key with an NSString holding the preferred_username from the OIDC id_token JWT, for use as login_hint on re-auth.
+extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyCustomHTTPHeaderName; //!< .userInfo key with an NSString holding the name of a custom HTTP header to attach to every request for this account.
+extern OCBookmarkUserInfoKey OCBookmarkUserInfoKeyCustomHTTPHeaderValue; //!< .userInfo key with an NSString holding the value of the custom HTTP header to attach to every request for this account.
 
 extern OCBookmarkCapability OCBookmarkCapabilityDrives; //!< This bookmark is drive-based.
 extern OCBookmarkCapability OCBookmarkCapabilityFavorites; //!< This bookmark supports favorites.
diff --git a/OpenCloudSDK/Bookmark/OCBookmark.m b/OpenCloudSDK/Bookmark/OCBookmark.m
index f1443e04..7167defc 100644
--- a/OpenCloudSDK/Bookmark/OCBookmark.m
+++ b/OpenCloudSDK/Bookmark/OCBookmark.m
@@ -628,6 +628,8 @@ + (OCIPCNotificationName)bookmarkAuthUpdateNotificationName
 OCBookmarkUserInfoKey OCBookmarkUserInfoKeyAllowHTTPConnection = @"OCAllowHTTPConnection";
 OCBookmarkUserInfoKey OCBookmarkUserInfoKeyBookmarkCreation = @"bookmark-creation";
 OCBookmarkUserInfoKey OCBookmarkUserInfoKeyPreferredUsername = @"preferred-username";
+OCBookmarkUserInfoKey OCBookmarkUserInfoKeyCustomHTTPHeaderName = @"custom-http-header-name";
+OCBookmarkUserInfoKey OCBookmarkUserInfoKeyCustomHTTPHeaderValue = @"custom-http-header-value";
 
 OCBookmarkCapability OCBookmarkCapabilityDrives = @"drives";
 OCBookmarkCapability OCBookmarkCapabilityFavorites = @"favorites";
diff --git a/OpenCloudSDK/Connection/OCConnection.m b/OpenCloudSDK/Connection/OCConnection.m
index af5997b1..64023e40 100644
--- a/OpenCloudSDK/Connection/OCConnection.m
+++ b/OpenCloudSDK/Connection/OCConnection.m
@@ -715,6 +715,16 @@ - (OCHTTPRequest *)pipeline:(OCHTTPPipeline *)pipeline prepareRequestForScheduli
 		[request addHeaderFields:_staticHeaderFields];
 	}
 
+	// Per-bookmark custom HTTP header (e.g. for reverse-proxy auth gating). See discussion opencloud-eu#2557.
+	NSString *customHeaderName = (NSString *)self.bookmark.userInfo[OCBookmarkUserInfoKeyCustomHTTPHeaderName];
+	NSString *customHeaderValue = (NSString *)self.bookmark.userInfo[OCBookmarkUserInfoKeyCustomHTTPHeaderValue];
+
+	if ([customHeaderName isKindOfClass:NSString.class] && (customHeaderName.length > 0) &&
+	    [customHeaderValue isKindOfClass:NSString.class] && (customHeaderValue.length > 0))
+	{
+		[request setValue:customHeaderValue forHeaderField:customHeaderName];
+	}
+
 	return (request);
 }