diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index d9318d8a9ba1..ea17dfb85baa 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -107,7 +107,7 @@ struct perf_session *perf_session__new(const char *filename, int mode,
 				       bool force, bool repipe,
 				       struct perf_tool *tool)
 {
-	size_t len = filename ? strlen(filename) + 1 : 0;
+	size_t len = filename ? strlen(filename) : 0;
 	struct perf_session *self = zalloc(sizeof(*self) + len);
 
 	if (self == NULL)
diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
index fb696124ad61..37bc38381fb6 100644
--- a/tools/perf/util/session.h
+++ b/tools/perf/util/session.h
@@ -50,7 +50,7 @@ struct perf_session {
 	int			cwdlen;
 	char			*cwd;
 	struct ordered_samples	ordered_samples;
-	char			filename[0];
+	char			filename[1];
 };
 
 struct perf_tool;