diff --git a/src/if_ruby.c b/src/if_ruby.c
index dd1ba47..aea7b56 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -178,9 +178,11 @@
 #define rb_hash_new			dll_rb_hash_new
 #define rb_inspect			dll_rb_inspect
 #define rb_int2inum			dll_rb_int2inum
+#if SIZEOF_INT < SIZEOF_LONG /* 64 bits only */
 #define rb_fix2int			dll_rb_fix2int
 #define rb_num2int			dll_rb_num2int
 #define rb_num2uint			dll_rb_num2uint
+#endif
 #define rb_lastline_get			dll_rb_lastline_get
 #define rb_lastline_set			dll_rb_lastline_set
 #define rb_load_protect			dll_rb_load_protect
@@ -271,9 +273,11 @@
 static VALUE (*dll_rb_hash_new) (void);
 static VALUE (*dll_rb_inspect) (VALUE);
 static VALUE (*dll_rb_int2inum) (long);
+#if SIZEOF_INT < SIZEOF_LONG /* 64 bits only */
 static long (*dll_rb_fix2int) (VALUE);
 static long (*dll_rb_num2int) (VALUE);
 static unsigned long (*dll_rb_num2uint) (VALUE);
+#endif
 static VALUE (*dll_rb_lastline_get) (void);
 static void (*dll_rb_lastline_set) (VALUE);
 static void (*dll_rb_load_protect) (VALUE, int, int*);
@@ -382,9 +386,11 @@
     {"rb_hash_new", (RUBY_PROC*)&dll_rb_hash_new},
     {"rb_inspect", (RUBY_PROC*)&dll_rb_inspect},
     {"rb_int2inum", (RUBY_PROC*)&dll_rb_int2inum},
+#if SIZEOF_INT < SIZEOF_LONG /* 64 bits only */
     {"rb_fix2int", (RUBY_PROC*)&dll_rb_fix2int},
     {"rb_num2int", (RUBY_PROC*)&dll_rb_num2int},
     {"rb_num2uint", (RUBY_PROC*)&dll_rb_num2uint},
+#endif
     {"rb_lastline_get", (RUBY_PROC*)&dll_rb_lastline_get},
     {"rb_lastline_set", (RUBY_PROC*)&dll_rb_lastline_set},
     {"rb_load_protect", (RUBY_PROC*)&dll_rb_load_protect},