diff --git a/etc/tak.scm b/etc/tak.scm
index 2a918d0e..69f4b5b0 100644
--- a/etc/tak.scm
+++ b/etc/tak.scm
@@ -1,3 +1,7 @@
+(import (scheme base)
+        (scheme time)
+        (scheme write))
+
 (define (time f)
   (let ((start (current-jiffy)))
     (f)
diff --git a/t/closure.scm b/t/closure.scm
index b74568e2..e747818b 100644
--- a/t/closure.scm
+++ b/t/closure.scm
@@ -1,3 +1,6 @@
+(import (scheme base)
+        (scheme write))
+
 (begin
 
  (define foo (lambda (a)
diff --git a/t/dynamic-wind.scm b/t/dynamic-wind.scm
index 7e8edaa6..f34f2213 100644
--- a/t/dynamic-wind.scm
+++ b/t/dynamic-wind.scm
@@ -1,3 +1,6 @@
+(import (scheme base)
+        (scheme write))
+
 (define (print obj)
   (write obj)
   (newline)
diff --git a/t/exception.scm b/t/exception.scm
index 86b244a9..ee92356b 100644
--- a/t/exception.scm
+++ b/t/exception.scm
@@ -1,3 +1,6 @@
+(import (scheme base)
+        (scheme write))
+
 (define (print obj)
   (write obj)
   (newline)
diff --git a/t/ir-macro.scm b/t/ir-macro.scm
index 28d4985c..a68806d6 100644
--- a/t/ir-macro.scm
+++ b/t/ir-macro.scm
@@ -1,3 +1,6 @@
+(import (scheme base)
+        (picrin macro))
+
 (define-syntax aif
   (ir-macro-transformer
    (lambda (form inject cmp)
diff --git a/t/letrec.scm b/t/letrec.scm
index 05e2e19e..435a15bf 100644
--- a/t/letrec.scm
+++ b/t/letrec.scm
@@ -1,3 +1,6 @@
+(import (scheme base)
+        (scheme write))
+
 (define (print obj)
   (write obj)
   (newline)
diff --git a/t/tailcall.scm b/t/tailcall.scm
index bbd14c2a..9c8cefd4 100644
--- a/t/tailcall.scm
+++ b/t/tailcall.scm
@@ -1,6 +1,10 @@
+(import (scheme base)
+        (scheme write))
+
 (define (sum k acc)
   (if (zero? k)
       acc
       (sum (- k 1) (+ k acc))))
 
-(display (sum 1000 0))
+(write (sum 1000 0))
+(newline)