PVS-Studio warning V645 for icu

#define uprv_strncat(dst, src, n) \
  U_STANDARD_CPP_NAMESPACE strncat(dst, src, n)

static char plugin_file[2048] = "";

U_CAPI void U_EXPORT2
uplug_init(UErrorCode *status)
{
  ....
  uprv_strncpy(plugin_file, plugin_dir, 2047);
  uprv_strncat(plugin_file, U_FILE_SEP_STRING,2047);
  uprv_strncat(plugin_file, "icuplugins",2047);
  uprv_strncat(plugin_file, U_ICU_VERSION_SHORT ,2047);
  uprv_strncat(plugin_file, ".txt" ,2047);
  ....
}

This suspicious code was found in icu project by PVS-Studio static code analyzer.
Warning message is:
V645 The 'strncat' function call could lead to the 'plugin_file' buffer overflow. The bounds should not contain the size of the buffer, but a number of characters it can hold. icuplug.c 739

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/