diff --git a/internal/sys.hpp b/internal/sys.hpp
index 98b6e5c..2975b8c 100644
--- a/internal/sys.hpp
+++ b/internal/sys.hpp
@@ -26,6 +26,7 @@
     virtual ~Sys() = default;
 
     virtual int open(const char* pathname, int flags) const = 0;
+    virtual int read(int fd, void* buf, std::size_t count) const = 0;
     virtual int close(int fd) const = 0;
     virtual void* mmap(void* addr, std::size_t length, int prot, int flags,
                        int fd, off_t offset) const = 0;
@@ -44,6 +45,7 @@
 {
   public:
     int open(const char* pathname, int flags) const override;
+    int read(int fd, void* buf, std::size_t count) const override;
     int close(int fd) const override;
     void* mmap(void* addr, std::size_t length, int prot, int flags, int fd,
                off_t offset) const override;