Compilation error with mingw: backslash removed from path, file not found then

Hello
I am compiling one altcoin for someone, and I am getting the following compilation error:

C:\altcoin>make -f Makefile.Release

g++ -c -pipe -O2 -frtti -fexceptions -mthreads -fdiagnostics-show-option -Wall -
Wextra -Wformat -Wformat-security -Wno-unused-parameter -DUNICODE -DQT_GUI -DBOO
ST_THREAD_USE_LIB -DBOOST_SPIRIT_THREADSAFE -DBOOST_THREAD_PROVIDES_GENERIC_SHAR
ED_MUTEX_ON_WIN -D__NO_SYSTEM_INCLUDES -DWIN32 -D_MT -DQT_DLL -DQT_NO_DEBUG -DQT
_GUI_LIB -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMX
EXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\Qt\4.8.5\include\Q
tCore" -I"..\Qt\4.8.5\include\QtGui" -I"..\Qt\4.8.5\include" -I"src" -I"src\json
" -I"src\qt" -I"..\deps\boost" -I"..\deps\db\build_unix" -I"..\deps\ssl\include"
-I"..\Qt\4.8.5\include\ActiveQt" -I"build" -I"build" -I"..\Qt\4.8.5\mkspecs\win
32-g++" -o build\bitcoin.o src\qt\bitcoin.cpp
g++.exe: error: srcqtbitcoin.cpp: No such file or directory
g++.exe: fatal error: no input files
compilation terminated.
make: *** [build/bitcoin.o] Error 1

This line is where the problem is:

g++.exe: error: srcqtbitcoin.cpp: No such file or directory

It seems that the make system or I don't know who mangled the file path from src\qt\bitcoin.cpp to srcqtbitcoin.cpp (backslashes are removed). Please don't you know how to fix this?