diff --git a/src/system.c b/src/system.c
index 9ae26c2..2315886 100644
--- a/src/system.c
+++ b/src/system.c
@@ -1493,6 +1493,24 @@ BOOL mock_WriteFile(HANDLE handle, char *src, DWORD len, DWORD *num, OVERLAPPED
     return WriteFile(desc->real_fd, src, len, num, ov);
 }
 
+DWORD mock_SetFilePointer(HANDLE hFile, LONG lDistanceToMove, PLONG lpDistanceToMoveHigh, DWORD dwMoveMethod)
+{
+    if (hFile == INVALID_HANDLE_VALUE || (int)hFile < 0 || (int)hFile >= MAX_DESCRIPTORS) {
+        SetLastError(ERROR_INVALID_HANDLE);
+        return INVALID_SET_FILE_POINTER;
+    }
+    int idx = (int) hFile;
+
+    Descriptor *desc = &current_process->desc[idx];
+    if (desc->type != DESC_FILE) {
+        SetLastError(ERROR_INVALID_HANDLE);
+        return INVALID_SET_FILE_POINTER;
+    }
+
+    // Forward to real SetFilePointer, last error is set by the real call
+    return SetFilePointer(desc->real_fd, lDistanceToMove, lpDistanceToMoveHigh, dwMoveMethod);
+}
+
 BOOL mock_GetFileSizeEx(HANDLE handle, LARGE_INTEGER *buf)
 {
     if (handle == INVALID_HANDLE_VALUE || (int)handle < 0 || (int)handle >= MAX_DESCRIPTORS) {
@@ -1785,6 +1803,24 @@ int mock_write(int fd, char *src, int len)
     }
 }
 
+off_t mock_lseek(int fd, off_t offset, int whence)
+{
+    if (fd < 0 || fd >= MAX_DESCRIPTORS) {
+        errno = EBADF;  // Bad file descriptor
+        return -1;
+    }
+    int idx = fd;
+
+    Descriptor *desc = &current_process->desc[idx];
+    if (desc->type != DESC_FILE) {
+        errno = EBADF;  // Not a file descriptor
+        return -1;
+    }
+
+    // Forward to real lseek, errno is set by the real call
+    return lseek(desc->real_fd, offset, whence);
+}
+
 int mock_fstat(int fd, struct stat *buf)
 {
     if (fd < 0 || fd >= MAX_DESCRIPTORS) {
diff --git a/src/system.h b/src/system.h
index 31ba995..b382e3d 100644
--- a/src/system.h
+++ b/src/system.h
@@ -65,6 +65,7 @@ BOOL     mock_UnlockFile(HANDLE hFile, DWORD dwFileOffsetLow, DWORD dwFileOffset
 BOOL     mock_FlushFileBuffers(HANDLE handle);
 BOOL     mock_ReadFile(HANDLE handle, char *dst, DWORD len, DWORD *num, OVERLAPPED *ov);
 BOOL     mock_WriteFile(HANDLE handle, char *src, DWORD len, DWORD *num, OVERLAPPED *ov);
+DWORD    mock_SetFilePointer(HANDLE hFile, LONG lDistanceToMove, PLONG lpDistanceToMoveHigh, DWORD dwMoveMethod);
 BOOL     mock_GetFileSizeEx(HANDLE handle, LARGE_INTEGER *buf);
 BOOL     mock_QueryPerformanceCounter(LARGE_INTEGER *lpPerformanceCount);
 BOOL     mock_QueryPerformanceFrequency(LARGE_INTEGER *lpFrequency);
@@ -81,6 +82,7 @@ int     mock_flock(int fd, int op);
 int     mock_fsync(int fd);
 int     mock_read(int fd, char *dst, int len);
 int     mock_write(int fd, char *src, int len);
+off_t   mock_lseek(int fd, off_t offset, int whence);
 int     mock_fstat(int fd, struct stat *buf);
 int     mock_mkstemp(char *path);
 char*   mock_realpath(char *path, char *dst);
@@ -117,6 +119,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_FlushFileBuffers mock_FlushFileBuffers
 #define sys_ReadFile         mock_ReadFile
 #define sys_WriteFile        mock_WriteFile
+#define sys_SetFilePointer   mock_SetFilePointer
 #define sys_GetFileSizeEx    mock_GetFileSizeEx
 #define sys__fullpath        mock__fullpath
 #define sys_QueryPerformanceCounter   mock_QueryPerformanceCounter
@@ -133,6 +136,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_fsync            mock_fsync
 #define sys_read             mock_read
 #define sys_write            mock_write
+#define sys_lseek            mock_lseek
 #define sys_fstat            mock_fstat
 #define sys_mkstemp          mock_mkstemp
 #define sys_realpath         mock_realpath
@@ -171,6 +175,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_FlushFileBuffers FlushFileBuffers
 #define sys_ReadFile         ReadFile
 #define sys_WriteFile        WriteFile
+#define sys_SetFilePointer   SetFilePointer
 #define sys_GetFileSizeEx    GetFileSizeEx
 #define sys__fullpath        _fullpath
 #define sys_QueryPerformanceCounter   QueryPerformanceCounter
@@ -187,6 +192,7 @@ int     mock_closedir(DIR *dirp);
 #define sys_fsync            fsync
 #define sys_read             read
 #define sys_write            write
+#define sys_lseek            lseek
 #define sys_fstat            fstat
 #define sys_mkstemp          mkstemp
 #define sys_realpath         realpath