diff --git a/sysfs/sysfswrite.hpp b/sysfs/sysfswrite.hpp
index 9f7083c..989f800 100644
--- a/sysfs/sysfswrite.hpp
+++ b/sysfs/sysfswrite.hpp
@@ -13,7 +13,8 @@
 class SysFsWritePercent : public WriteInterface
 {
     public:
-        SysFsWritePercent(std::string& writepath, int64_t min, int64_t max)
+        SysFsWritePercent(const std::string& writepath, int64_t min,
+                          int64_t max)
             : WriteInterface(min, max),
               _writepath(FixupPath(writepath))
         { }
@@ -27,7 +28,7 @@
 class SysFsWrite : public WriteInterface
 {
     public:
-        SysFsWrite(std::string& writepath, int64_t min, int64_t max)
+        SysFsWrite(const std::string& writepath, int64_t min, int64_t max)
             : WriteInterface(min, max),
               _writepath(FixupPath(writepath))
         { }