diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 21fa781b03cc..1fab00ec4a59 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -448,6 +448,12 @@ static int get_max_num(char *path, int *max)
 
 	buf[num] = '\0';
 
+	/* empty file — nothing to parse */
+	if (num == 0) {
+		err = -1;
+		goto out;
+	}
+
 	/* start on the right, to find highest node num */
 	while (--num) {
 		if ((buf[num] == ',') || (buf[num] == '-')) {