diff --git a/tools/perf/util/units.c b/tools/perf/util/units.c
index a46762aec4c9..24c83b8b8c98 100644
--- a/tools/perf/util/units.c
+++ b/tools/perf/util/units.c
@@ -57,7 +57,7 @@ unsigned long convert_unit(unsigned long value, char *unit)
 
 int unit_number__scnprintf(char *buf, size_t size, u64 n)
 {
-	char unit[4] = "BKMG";
+	char unit[] = "BKMG";
 	int i = 0;
 
 	while (((n / 1024) > 1) && (i < 3)) {