--- revision.cc
+++ revision.cc
@@ -336,7 +336,8 @@
         {
           L(F("found node %d, ancestor of left %s and right %s\n")
             % anc % left % right);
+	  return true;
         }
     }
 //      dump_bitset_map("ancestors", ancestors);
--- tests/t_diff_direct_ancestor.at
+++ tests/t_diff_direct_ancestor.at
@@ -0,1 +1,27 @@
+AT_SETUP([add file, commit, change, commit, diff])
+
+# This test is a bug report.
+AT_XFAIL_IF(true)
+
+MONOTONE_SETUP
+
+AT_DATA(v1a, [foo blah
+])
+AT_DATA(v1b, [bar blah
+])
+AT_DATA(v2a, [baz blah
+])
+
+AT_CHECK(cp v1a testfile)
+AT_CHECK(MONOTONE add testfile, [], [ignore], [ignore])
+COMMIT(testbranch)
+BASE_R_SHA=`BASE_REVISION`
+
+AT_CHECK(cp v1b testfile)
+COMMIT(testbranch)
+CHILD_R_SHA=`BASE_REVISION`
+
+AT_CHECK(MONOTONE diff $BASE_R_SHA $CHILD_R_SHA, [], [ignore], [ignore])
+
+AT_CLEANUP
--- testsuite.at
+++ testsuite.at
@@ -312,3 +312,4 @@
 m4_include(tests/t_rcfile_required.at)
 m4_include(tests/t_persistent_server_revision.at)
 m4_include(tests/t_persistent_server_keys.at)
+m4_include(tests/t_diff_direct_ancestor.at)