1 files changed, 2 insertions, 2 deletions
diff --git a/rubyio.h b/rubyio.h
index 036f24426c..77c37fc45f 100644
--- a/rubyio.h
+++ b/rubyio.h
@@ -48,8 +48,8 @@ typedef struct OpenFile {
 #define GetReadFile(fptr) ((fptr)->f)
 #define GetWriteFile(fptr) (((fptr)->f2) ? (fptr)->f2 : (fptr)->f)
 
-FILE *rb_fopen _((char *, char *));
-FILE *rb_fdopen _((int, char *));
+FILE *rb_fopen _((const char*, const char*));
+FILE *rb_fdopen _((int, const char*));
 void rb_io_check_writable _((OpenFile *));
 void rb_io_check_readable _((OpenFile *));
 void rb_io_fptr_finalize _((OpenFile *));