diff --git a/Makefile b/Makefile
index 48209640..cb4c9d7b 100644
--- a/Makefile
+++ b/Makefile
@@ -46,7 +46,7 @@ REPL_ISSUE_TESTS = $(wildcard t/issue/*.sh)
 
 TEST_RUNNER = picrin
 
-CFLAGS += -I./lib -I./lib/include -Wall -Wextra
+CFLAGS += -I./lib/include -Wall -Wextra
 LDFLAGS += -lm
 
 prefix ?= /usr/local
diff --git a/lib/ext/eval.c b/lib/ext/eval.c
index 9da69c51..693ccf8f 100644
--- a/lib/ext/eval.c
+++ b/lib/ext/eval.c
@@ -4,9 +4,9 @@
 
 #include "picrin.h"
 #include "picrin/extra.h"
-#include "object.h"
-#include "state.h"
-#include "vm.h"
+#include "../object.h"
+#include "../state.h"
+#include "../vm.h"
 
 pic_value pic_expand(pic_state *pic, pic_value expr, pic_value env);
 
diff --git a/lib/ext/read.c b/lib/ext/read.c
index 26829413..d20e9ff6 100644
--- a/lib/ext/read.c
+++ b/lib/ext/read.c
@@ -4,7 +4,7 @@
 
 #include "picrin.h"
 #include "picrin/extra.h"
-#include "object.h"
+#include "../object.h"
 
 #undef EOF
 #define EOF (-1)
diff --git a/lib/ext/write.c b/lib/ext/write.c
index 510fb6ae..076344c4 100644
--- a/lib/ext/write.c
+++ b/lib/ext/write.c
@@ -4,7 +4,7 @@
 
 #include "picrin.h"
 #include "picrin/extra.h"
-#include "object.h"
+#include "../object.h"
 
 struct writer_control {
   int mode;