diff --git a/SoObjects/Appointments/SOGoAppointmentFolder.m b/SoObjects/Appointments/SOGoAppointmentFolder.m
index 8d5e05aa1..a5806d996 100644
--- a/SoObjects/Appointments/SOGoAppointmentFolder.m
+++ b/SoObjects/Appointments/SOGoAppointmentFolder.m
@@ -3076,15 +3076,15 @@ firstInstanceCalendarDateRange: (NGCalendarDateRange *) fir
 }
 
 /* folder management */
-- (BOOL) create
+- (NSException *) create
 {
-  BOOL rc;
   SOGoUserSettings *userSettings;
   NSMutableDictionary *calendarSettings;
+  NSException *error;
   SOGoUser *ownerUser;
 
-  rc = [super create];
-  if (rc)
+  error = [super create];
+  if (!error)
     {
       ownerUser = [SOGoUser userWithLogin: [self ownerInContext: context]];
       userSettings = [ownerUser userSettings];
@@ -3097,7 +3097,7 @@ firstInstanceCalendarDateRange: (NGCalendarDateRange *) fir
       [userSettings synchronize];
     }
 
-  return rc;
+  return error;
 }
 
 - (void) removeFolderSettings: (NSMutableDictionary *) moduleSettings
diff --git a/SoObjects/Appointments/SOGoAppointmentFolders.m b/SoObjects/Appointments/SOGoAppointmentFolders.m
index b8639c0f1..aa13063f8 100644
--- a/SoObjects/Appointments/SOGoAppointmentFolders.m
+++ b/SoObjects/Appointments/SOGoAppointmentFolders.m
@@ -398,20 +398,18 @@ static SoSecurityManager *sm = nil;
   if ([subfolderNames containsObject: newName])
     {
       content = [NSString stringWithFormat: @"A collection named '%@' already exists.", newName];
-      error = [NSException exceptionWithDAVStatus: 403
+      error = [NSException exceptionWithDAVStatus: 405
                                            reason: content];
     }
   else
     {
-      properties = [[createContext request]
-		     davPatchedPropertiesWithTopTag: @"mkcalendar"];
+      properties = [[createContext request] davPatchedPropertiesWithTopTag: @"mkcalendar"];
       setProperties = [properties objectForKey: @"set"];
       newDisplayName = [self _fetchPropertyWithName: @"{DAV:}displayname"
                                             inArray: setProperties];
       if (![newDisplayName length])
 	newDisplayName = newName;
-      error
-	= [self newFolderWithName: newDisplayName andNameInContainer: newName];
+      error = [self newFolderWithName: newDisplayName andNameInContainer: newName];
       if (!error)
 	{
 	  newFolder = [self lookupName: newName
diff --git a/SoObjects/SOGo/SOGoGCSFolder.h b/SoObjects/SOGo/SOGoGCSFolder.h
index 6a3f56fa7..a5d0c7a13 100644
--- a/SoObjects/SOGo/SOGoGCSFolder.h
+++ b/SoObjects/SOGo/SOGoGCSFolder.h
@@ -1,6 +1,6 @@
 /*
   Copyright (C) 2004-2005 SKYRIX Software AG
-  Copyright (C) 2006-2015 Inverse inc.
+  Copyright (C) 2006-2022 Inverse inc.
 
   This file is part of SOGo.
 
@@ -96,7 +96,7 @@
 
 - (BOOL) folderIsMandatory;
 
-- (BOOL) create;
+- (NSException *) create;
 - (NSException *) delete;
 - (void) renameTo: (NSString *) newName;
 
diff --git a/SoObjects/SOGo/SOGoGCSFolder.m b/SoObjects/SOGo/SOGoGCSFolder.m
index d2ac21d66..2b1bf55a8 100644
--- a/SoObjects/SOGo/SOGoGCSFolder.m
+++ b/SoObjects/SOGo/SOGoGCSFolder.m
@@ -556,7 +556,7 @@ static NSArray *childRecordFields = nil;
 	  && [userLogin isEqualToString: [self ownerInContext: context]]
           && [user canAuthenticate]
 	  && [self folderIsMandatory]
-	  && [self create])
+	  && ![self create])
 	ocsFolder = [self ocsFolderForPath: [self ocsPath]];
       [ocsFolder retain];
     }
@@ -569,7 +569,7 @@ static NSArray *childRecordFields = nil;
   return folder;
 }
 
-- (BOOL) create
+- (NSException *) create
 {
   NSException *result;
   result = [[self folderManager] createFolderOfType: [self folderType]
@@ -580,7 +580,7 @@ static NSArray *childRecordFields = nil;
       && [[context request] handledByDefaultHandler])
     [self sendFolderAdvisoryTemplate: @"Addition"];
 
-  return (result == nil);
+  return result;
 }
 
 - (NSException *) delete
diff --git a/SoObjects/SOGo/SOGoObject.m b/SoObjects/SOGo/SOGoObject.m
index 9de8fe230..277b9d8ca 100644
--- a/SoObjects/SOGo/SOGoObject.m
+++ b/SoObjects/SOGo/SOGoObject.m
@@ -413,7 +413,7 @@
   davPrivileges = [NSMutableArray array];
 
   privileges = [[webdavAclManager davPermissionsForRoles: roles
-				  onObject: self] objectEnumerator];
+                                                onObject: self] objectEnumerator];
   while ((privilege = [privileges nextObject]))
     [davPrivileges addObject: davElementWithContent (@"privilege", XMLNS_WEBDAV,
 						     privilege)];
diff --git a/SoObjects/SOGo/SOGoParentFolder.m b/SoObjects/SOGo/SOGoParentFolder.m
index 67ecba927..e39022662 100644
--- a/SoObjects/SOGo/SOGoParentFolder.m
+++ b/SoObjects/SOGo/SOGoParentFolder.m
@@ -178,7 +178,7 @@ static SoSecurityManager *sm = nil;
       [folder setDisplayName: [self defaultFolderName]];
       [folder setOCSPath: [NSString stringWithFormat: @"%@/%@", OCSPath, folderName]];
       
-      if ([folder create])
+      if (![folder create])
         [subFolders setObject: folder forKey: folderName];
     }
     else if (folderType == SOGoCollectedFolder)
@@ -190,7 +190,7 @@ static SoSecurityManager *sm = nil;
         [folder setDisplayName: [self collectedFolderName]];
         [folder setOCSPath: [NSString stringWithFormat: @"%@/%@", OCSPath, folderName]];
         
-        if ([folder create])
+        if (![folder create])
           [subFolders setObject: folder forKey: folderName];
         
         [ud setSelectedAddressBook:folderName];
@@ -406,14 +406,23 @@ static SoSecurityManager *sm = nil;
       [newFolder setDisplayName: name];
       [newFolder setOCSPath: [NSString stringWithFormat: @"%@/%@",
                                        OCSPath, newNameInContainer]];
-      if ([newFolder create])
+      error = [newFolder create];
+      if (!error)
 	{
 	  [subFolders setObject: newFolder forKey: newNameInContainer];
 	  error = nil;
 	}
+      else if ([[error name] isEqual: @"GCSExitingFolder"])
+        {
+          error = [self exceptionWithHTTPStatus: 405
+                                         reason: [error reason]];
+        }
       else
-        error = [self exceptionWithHTTPStatus: 400
-                                       reason: @"The new folder could not be created"];
+        {
+          [self errorWithFormat: @"An error occured when creating a folder: %@ - %@", [error name], [error reason]];
+          error = [self exceptionWithHTTPStatus: 400
+                                         reason: @"The new folder could not be created"];
+        }
     }
 
   return error;
diff --git a/Tests/spec/CalDAVPropertiesSpec.js b/Tests/spec/CalDAVPropertiesSpec.js
index a0f2af15e..0c9ddb000 100644
--- a/Tests/spec/CalDAVPropertiesSpec.js
+++ b/Tests/spec/CalDAVPropertiesSpec.js
@@ -15,6 +15,13 @@ describe('read and set calendar properties', function() {
     await webdav.deleteObject(resource)
   })
 
+  it("calendar already exists", async function() {
+    const response = await webdav.makeCalendar(resource)
+    expect(response[0].status)
+      .withContext(`HTTP status code of MKCALENDAR`)
+      .toEqual(405)
+  })
+
   // CalDAVPropertiesTest
 
   it("propfind", async function() {
diff --git a/Tests/spec/CardDAVSpec.js b/Tests/spec/CardDAVSpec.js
index c83667cf6..f57a1e09c 100644
--- a/Tests/spec/CardDAVSpec.js
+++ b/Tests/spec/CardDAVSpec.js
@@ -97,6 +97,13 @@ describe('CardDAV extensions', function() {
     await webdav_su.deleteObject(resource)
   })
 
+  it("addressbook already exists", async function() {
+    const response = await webdav.makeCollection(resource)
+    expect(response[0].status)
+      .withContext(`HTTP status code of MKCOL`)
+      .toEqual(405)
+  })
+
   // CARDDAV:addressbook-query Report
   // https://datatracker.ietf.org/doc/html/rfc6352#section-8.6
   it("supports for addressbook-query on GCS folder", async function() {