diff --git a/fs/cpuacct.go b/fs/cpuacct.go
index 391a023..dd5d7c9 100644
--- a/fs/cpuacct.go
+++ b/fs/cpuacct.go
@@ -133,7 +133,10 @@ func getPercpuUsageInModes(path string) ([]uint64, []uint64, error) {
 
 	for scanner.Scan() {
 		// Each line is: cpu user system
-		fields := strings.SplitN(scanner.Text(), " ", 3)
+		// Keep 'n' at 4 — downstream changes or refactoring of
+		// "cpuacct.usage_all" could otherwise break system usage parsing.
+		// (issue: https://github.com/opencontainers/cgroups/issues/46)
+		fields := strings.SplitN(scanner.Text(), " ", 4)
 		if len(fields) != 3 {
 			continue
 		}
diff --git a/fs/cpuacct_test.go b/fs/cpuacct_test.go
index c0c9543..2c82756 100644
--- a/fs/cpuacct_test.go
+++ b/fs/cpuacct_test.go
@@ -20,6 +20,7 @@ const (
 	5 872544369885276 638763309884944
 	6 870104915696359 640081778921247
 	7 870202363887496 638716766259495
+	8 867579076304580 988021047245223 792312716071280 109505081909990
 	`
 )