diff --git a/contrib/03.file/nitro.mk b/contrib/03.file/nitro.mk
deleted file mode 100644
index d6bcbd93..00000000
--- a/contrib/03.file/nitro.mk
+++ /dev/null
@@ -1,2 +0,0 @@
-CONTRIB_INITS += file
-CONTRIB_SRCS += $(wildcard contrib/03.file/src/*.c)
diff --git a/contrib/03.load/nitro.mk b/contrib/03.load/nitro.mk
deleted file mode 100644
index 87566d36..00000000
--- a/contrib/03.load/nitro.mk
+++ /dev/null
@@ -1,2 +0,0 @@
-CONTRIB_INITS += load
-CONTRIB_SRCS += $(wildcard contrib/03.load/src/*.c)
diff --git a/contrib/03.mutable-string/nitro.mk b/contrib/03.mutable-string/nitro.mk
deleted file mode 100644
index 37d31b55..00000000
--- a/contrib/03.mutable-string/nitro.mk
+++ /dev/null
@@ -1,2 +0,0 @@
-CONTRIB_INITS += mutable_string
-CONTRIB_SRCS += $(wildcard contrib/03.mutable-string/*.c)
diff --git a/contrib/03.system/nitro.mk b/contrib/03.system/nitro.mk
deleted file mode 100644
index e9553587..00000000
--- a/contrib/03.system/nitro.mk
+++ /dev/null
@@ -1,2 +0,0 @@
-CONTRIB_INITS += system
-CONTRIB_SRCS += $(wildcard contrib/03.system/src/*.c)
diff --git a/contrib/03.time/nitro.mk b/contrib/03.time/nitro.mk
deleted file mode 100644
index 61b7c4d3..00000000
--- a/contrib/03.time/nitro.mk
+++ /dev/null
@@ -1,2 +0,0 @@
-CONTRIB_INITS += time
-CONTRIB_SRCS += $(wildcard contrib/03.time/src/*.c)
diff --git a/contrib/05.r7rs/nitro.mk b/contrib/05.r7rs/nitro.mk
index b811b92e..56bf8f2f 100644
--- a/contrib/05.r7rs/nitro.mk
+++ b/contrib/05.r7rs/nitro.mk
@@ -1,3 +1,13 @@
+CONTRIB_INITS += r7rs
+
+CONTRIB_SRCS += \
+	contrib/05.r7rs/src/r7rs.c\
+	contrib/05.r7rs/src/file.c\
+	contrib/05.r7rs/src/load.c\
+	contrib/05.r7rs/src/mutable-string.c\
+	contrib/05.r7rs/src/system.c\
+	contrib/05.r7rs/src/time.c
+
 CONTRIB_LIBS += \
 	contrib/05.r7rs/scheme/base.scm\
 	contrib/05.r7rs/scheme/cxr.scm\
diff --git a/contrib/03.file/src/file.c b/contrib/05.r7rs/src/file.c
similarity index 100%
rename from contrib/03.file/src/file.c
rename to contrib/05.r7rs/src/file.c
diff --git a/contrib/03.load/src/load.c b/contrib/05.r7rs/src/load.c
similarity index 100%
rename from contrib/03.load/src/load.c
rename to contrib/05.r7rs/src/load.c
diff --git a/contrib/03.mutable-string/mutable-string.c b/contrib/05.r7rs/src/mutable-string.c
similarity index 100%
rename from contrib/03.mutable-string/mutable-string.c
rename to contrib/05.r7rs/src/mutable-string.c
diff --git a/contrib/05.r7rs/src/r7rs.c b/contrib/05.r7rs/src/r7rs.c
new file mode 100644
index 00000000..ad3090aa
--- /dev/null
+++ b/contrib/05.r7rs/src/r7rs.c
@@ -0,0 +1,21 @@
+/**
+ * See Copyright Notice in picrin.h
+ */
+
+#include "picrin.h"
+
+void pic_init_file(pic_state *);
+void pic_init_load(pic_state *);
+void pic_init_mutable_string(pic_state *);
+void pic_init_system(pic_state *);
+void pic_init_time(pic_state *);
+
+void
+pic_init_r7rs(pic_state *pic)
+{
+  pic_init_file(pic);
+  pic_init_load(pic);
+  pic_init_mutable_string(pic);
+  pic_init_system(pic);
+  pic_init_time(pic);
+}
diff --git a/contrib/03.system/src/system.c b/contrib/05.r7rs/src/system.c
similarity index 100%
rename from contrib/03.system/src/system.c
rename to contrib/05.r7rs/src/system.c
diff --git a/contrib/03.time/src/time.c b/contrib/05.r7rs/src/time.c
similarity index 100%
rename from contrib/03.time/src/time.c
rename to contrib/05.r7rs/src/time.c