diff --git a/include/picrin.h b/include/picrin.h
index 0120d3cd..fd4c8f56 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -211,6 +211,7 @@ NORETURN void pic_errorf(pic_state *, const char *, size_t, ...);
 void pic_warn(pic_state *, const char *);
 
 void pic_debug(pic_state *, pic_value);
+void pic_fdebug(pic_state *, pic_value, XFILE *);
 
 #if defined(__cplusplus)
 }
diff --git a/src/write.c b/src/write.c
index f8629881..4925d52a 100644
--- a/src/write.c
+++ b/src/write.c
@@ -157,8 +157,14 @@ write(pic_state *pic, pic_value obj, XFILE *file)
 void
 pic_debug(pic_state *pic, pic_value obj)
 {
-  write(pic, obj, xstdout);
-  xfflush(xstdout);
+  pic_fdebug(pic, obj, xstdout);
+}
+
+void
+pic_fdebug(pic_state *pic, pic_value obj, XFILE *file)
+{
+  write(pic, obj, file);
+  xfflush(file);
 }
 
 static pic_value