--- CMakeLists.txt.orig	2020-10-03 08:02:55 UTC
+++ CMakeLists.txt
@@ -2,7 +2,7 @@
 # Copyright (c) 2007 - 2018 Michal Cihar
 # vim: expandtab sw=4 ts=4 sts=4:
 
-cmake_minimum_required (VERSION 3.0)
+cmake_minimum_required (VERSION 3.5)
 INCLUDE (CMakeForceCompiler)
 
 project (Gammu C)
@@ -123,7 +123,7 @@ check_symbol_exists (getuid "unistd.h" HAVE_GETUID)
 check_symbol_exists (getgrnam "grp.h" HAVE_GETGRNAM)
 check_symbol_exists (getpwuid "pwd.h" HAVE_GETPWUID)
 check_symbol_exists (getuid "unistd.h" HAVE_GETUID)
-check_symbol_exists (initgroups "grp.h" HAVE_INITGROUPS)
+check_symbol_exists (initgroups "unistd.h" HAVE_INITGROUPS)
 check_symbol_exists (setuid "unistd.h" HAVE_SETUID)
 check_symbol_exists (setgid "unistd.h" HAVE_SETGID)
 check_symbol_exists (SIGHUP "signal.h" HAVE_SIGHUP)
@@ -446,7 +446,6 @@ if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_MINGW 
     #
     # Warnings related flags
     #
-    MACRO_TUNE_COMPILER("-O2")
     MACRO_TUNE_COMPILER("-Wall")
     MACRO_TUNE_COMPILER("-Werror-implicit-function-declaration")
     MACRO_TUNE_COMPILER("-Wno-deprecated-declarations")
@@ -568,7 +567,6 @@ set (DOCS
 set (DOCS
     README.rst
     ChangeLog
-    COPYING
     )
 
 if (CMAKE_USE_PTHREADS_INIT)
