diff --git a/ChangeLog b/ChangeLog
index 8684e5f6f..e91bb16d2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2007-10-26  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
 
+	* SoObjects/Mailer/SOGoMailBodyPart.m ([SOGoMailBodyPart
+	-GETAction:]): use the "application/octet-stream" mime type for
+	elements of type "application/x-xpinstall" to avoid confusing
+	Firefox.
+
 	* UI/PreferencesUI/UIxPreferences.m ([UIxPreferences -messageCheckList])
 	([UIxPreferences -itemMessageCheckText])
 	([UIxPreferences -userMessageCheck])
diff --git a/SoObjects/Mailer/SOGoMailBodyPart.m b/SoObjects/Mailer/SOGoMailBodyPart.m
index fb11b0191..d1a1f42fe 100644
--- a/SoObjects/Mailer/SOGoMailBodyPart.m
+++ b/SoObjects/Mailer/SOGoMailBodyPart.m
@@ -258,7 +258,7 @@ static BOOL debugOn = NO;
   NSException *error;
   WOResponse *r;
   NSData     *data;
-  NSString   *etag;
+  NSString   *etag, *mimeType;
   
   if ((error = [self matchesRequestConditionInContext:_ctx]) != nil) {
     // TODO: currently we fetch the body structure to get here - check this!
@@ -283,14 +283,19 @@ static BOOL debugOn = NO;
   
   // TODO: wrong, could be encoded
   r = [(WOContext *)_ctx response];
-  [r setHeader:[self davContentType] forKey:@"content-type"];
-  [r setHeader:[NSString stringWithFormat:@"%d", [data length]]
-     forKey:@"content-length"];
-  
+  mimeType = [self davContentType];
+  if ([mimeType isEqualToString: @"application/x-xpinstall"])
+    mimeType = @"application/octet-stream";
+
+  [r setHeader: mimeType forKey:@"content-type"];
+  [r setHeader: [NSString stringWithFormat:@"%d", [data length]]
+     forKey: @"content-length"];
+
   if ((etag = [self davEntityTag]) != nil)
     [r setHeader:etag forKey:@"etag"];
 
   [r setContent:data];
+
   return r;
 }