diff --git a/src/Makefile b/src/Makefile
index b956219..2985e4e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -33,7 +33,7 @@ c99.o: c99.c common.h code.h parser.h ../include/C99.h
 	$(CC) $(c99_CFLAGS) -c c99.c
 
 code.o: code.c ../include/C99/target.h code.h ../config.h
-	$(CC) $(c99_CFLAGS) -c code.c
+	$(CC) -D PREFIX=\"$(PREFIX)\" $(c99_CFLAGS) -c code.c
 
 main.o: main.c ../include/C99.h ../config.h
 	$(CC) $(c99_CFLAGS) -c main.c
diff --git a/src/project.conf b/src/project.conf
index f374e7a..8227042 100644
--- a/src/project.conf
+++ b/src/project.conf
@@ -17,6 +17,7 @@ depends=common.h,code.h,parser.h,../include/C99.h
 
 [code.c]
 depends=../include/C99/target.h,code.h,../config.h
+cppflags=-D PREFIX=\"$(PREFIX)\"
 
 [main.c]
 depends=../include/C99.h,../config.h