diff --git a/tools/ovl_offset.pl b/tools/ovl_offset.pl
index 89c3468556..10419999d6 100755
--- a/tools/ovl_offset.pl
+++ b/tools/ovl_offset.pl
@@ -4,6 +4,10 @@
 # on a reference map file (.refmap)
 
 sub map_scan {
+    # The buflib handle table is a few hundred bytes, just before
+    # the plugin buffer. We assume it's never more than 1024 bytes.
+    # If this assumption is wrong, overlay loading will fail.
+    my $max_handle_table_size = 1024;
     my ($map) = @_;
     my $ramstart = -1, $ramsize = -1, $startaddr = -1, $endaddr = -1;
     open (MAP, "<$map");
@@ -25,7 +29,7 @@ sub map_scan {
         printf "Could not analyze map file.\n";
         exit 1;
     }
-    return $ramstart + $ramsize - $endaddr;
+    return $ramstart + $ramsize - $endaddr - $max_handle_table_size;
 }
 
 printf map_scan($ARGV[0]) & ~0xf;