Use pkg-config to detect cflags
--- a/src/makefile
+++ b/src/makefile
@@ -170,11 +170,13 @@ SOCKET_macosx=usocket.o
 #------
 # Compiler and linker settings
 # for Linux
+LUAPC=lua$(LUAV)
+LUA_CFLAGS=$(shell pkg-config --cflags $(LUAPC))
 SO_linux=so
 O_linux=o
 CC_linux=gcc
 DEF_linux=-DLUASOCKET_$(DEBUG)
-CFLAGS_linux=$(LUAINC:%=-I%) $(DEF) -Wall -Wshadow -Wextra \
+CFLAGS_linux=$(LUA_CFLAGS) $(LUAINC:%=-I%) $(DEF) -Wall -Wshadow -Wextra \
 	-Wimplicit -O2 -ggdb3 -fpic
 LDFLAGS_linux=-O -shared -fpic -o
 LD_linux=gcc