diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index 3a1d94d..207e860 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -33,7 +33,7 @@
 		return -ENOMEM;
 
 	if (hit)
-		he->count += count;
+		__perf_session__add_count(he, al, count);
 
 	return 0;
 }
@@ -225,6 +225,10 @@
 			input_new = argv[1];
 		} else
 			input_new = argv[0];
+	} else if (symbol_conf.default_guest_vmlinux_name ||
+		   symbol_conf.default_guest_kallsyms) {
+		input_old = "perf.data.host";
+		input_new = "perf.data.guest";
 	}
 
 	symbol_conf.exclude_other = false;