Fixed typo.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@10360 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/drd_main.c b/drd/drd_main.c
index 4c60866..2ca6f88 100644
--- a/drd/drd_main.c
+++ b/drd/drd_main.c
@@ -138,7 +138,7 @@
    }
    if (segment_merging != -1)
       DRD_(thread_set_segment_merging)(segment_merging);
-   if (segment_merge_interval != 1)
+   if (segment_merge_interval != -1)
       DRD_(thread_set_segment_merge_interval)(segment_merge_interval);
    if (show_confl_seg != -1)
       DRD_(set_show_conflicting_segments)(show_confl_seg);