diff --git a/ChangeLog b/ChangeLog
index d30197a20..c4edd2f97 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2011-07-27  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
 
+	* OpenChange/SOGoMAPIFSMessage.m (-save): serialize the properties
+	dictionary in binary plist format to avoid GNUstep bugs where
+	high unsigned long long values are not parsed properly.
+	(-properties): corrolary to the above change.
+
 	* OpenChange/NSArray+MAPIStore.m (-asArrayOfUnicodeStringsInCtx:):
 	the return type is now "struct WStringArray_r *".
 
diff --git a/OpenChange/SOGoMAPIFSMessage.m b/OpenChange/SOGoMAPIFSMessage.m
index 428e9a9d7..10c3fe19c 100644
--- a/OpenChange/SOGoMAPIFSMessage.m
+++ b/OpenChange/SOGoMAPIFSMessage.m
@@ -21,9 +21,11 @@
  */
 
 #import <Foundation/NSArray.h>
+#import <Foundation/NSData.h>
 #import <Foundation/NSDictionary.h>
 #import <Foundation/NSFileManager.h>
 #import <Foundation/NSException.h>
+#import <Foundation/NSPropertyList.h>
 #import <Foundation/NSString.h>
 
 #import <NGExtensions/NSObject+Logs.h>
@@ -66,10 +68,26 @@
 
 - (NSDictionary *) properties
 {
+  NSData *content;
+  NSString *error;
+  NSPropertyListFormat format;
+
   if (!properties)
     {
-      properties = [[NSMutableDictionary alloc]
-		     initWithContentsOfFile: [self completeFilename]];
+      content = [NSData dataWithContentsOfFile: [self completeFilename]];
+      if (content)
+        {
+          properties = [NSPropertyListSerialization propertyListFromData: content
+                                                        mutabilityOption: NSPropertyListMutableContainers
+                                                                  format: &format
+                                                        errorDescription: &error];
+          [properties retain];
+          if (!properties)
+            [self logWithFormat: @"an error occurred during deserialization"
+                  @" of message: '%@'", error];
+        }
+      else
+        properties = nil;
       if (!properties)
         properties = [NSMutableDictionary new];
     }
@@ -88,9 +106,14 @@
 
 - (void) save
 {
+  NSData *content;
+
   [container ensureDirectory];
 
-  if (![properties writeToFile: [self completeFilename] atomically: YES])
+  content = [NSPropertyListSerialization dataFromPropertyList: properties
+                                                       format: NSPropertyListBinaryFormat_v1_0
+                                             errorDescription: NULL];
+  if (![content writeToFile: [self completeFilename] atomically: NO])
     [NSException raise: @"MAPIStoreIOException"
 		 format: @"could not save message"];
 }