diff --git a/lcl/interfaces/gtk2/gtk2wsdialogs.pp b/lcl/interfaces/gtk2/gtk2wsdialogs.pp
index 59447a15c7..de8d6208ee 100644
--- a/lcl/interfaces/gtk2/gtk2wsdialogs.pp
+++ b/lcl/interfaces/gtk2/gtk2wsdialogs.pp
@@ -857,7 +857,10 @@ begin
 
       for k := 0 to MaskList.Count - 1 do begin
         aMask:=UTF8ToSys(MaskList.Strings[k]);
-        gtk_file_filter_add_pattern(GtkFilter, PChar(aMask));
+        if pos('/',aMask)>0 then
+          gtk_file_filter_add_mime_type(GtkFilter, PChar(aMask))
+        else
+          gtk_file_filter_add_pattern(GtkFilter, PChar(aMask));
       end;
 
       gtk_file_filter_set_name(GtkFilter, FilterEntry.Description);
diff --git a/lcl/interfaces/gtk3/gtk3wsdialogs.pp b/lcl/interfaces/gtk3/gtk3wsdialogs.pp
index 000515f92f..a16d6a0529 100644
--- a/lcl/interfaces/gtk3/gtk3wsdialogs.pp
+++ b/lcl/interfaces/gtk3/gtk3wsdialogs.pp
@@ -1108,6 +1108,9 @@ begin
       MaskList.DelimitedText := FilterEntry.Mask;
 
       for k := 0 to MaskList.Count - 1 do
+      if pos('/',MaskList.Strings[k])>0 then
+        gtk_file_filter_add_mime_type(GtkFilter, PgChar(MaskList.Strings[k]))
+      else
         gtk_file_filter_add_pattern(GtkFilter, PgChar(MaskList.Strings[k]));
       gtk_file_filter_set_name(GtkFilter, PgChar(FilterEntry.Description));