diff --git a/src/if_ruby.c b/src/if_ruby.c
index aea7b56..bc15b4a 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -336,11 +336,11 @@
 #endif
 
 #ifdef RUBY19_OR_LATER
-SIGNED_VALUE rb_num2long_stub(VALUE x)
+static SIGNED_VALUE rb_num2long_stub(VALUE x)
 {
     return dll_rb_num2long(x);
 }
-VALUE rb_int2big_stub(SIGNED_VALUE x)
+static VALUE rb_int2big_stub(SIGNED_VALUE x)
 {
     return dll_rb_int2big(x);
 }