diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index d293e55553bd..ba7aaf421f36 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1423,7 +1423,8 @@ nr_pages_store(struct device *dev, struct device_attribute *attr,
 		if (!end)
 			break;
 
-		len -= end - p;
+		/* consume the number and the following comma, hence +1 */
+		len -= end - p + 1;
 		p = end + 1;
 	} while (len);