diff --git a/src/if_ruby.c b/src/if_ruby.c
index 9c91f31..e53e0ef 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -476,7 +476,11 @@ static void (*dll_ruby_init_stack)(VALUE*);
 #  endif
 # endif
 # ifdef RUBY19_OR_LATER
+#  ifdef DYNAMIC_RUBY_VER >= 26
+static VALUE (*dll_rb_int2big)(intptr_t);
+#  else
 static VALUE (*dll_rb_int2big)(SIGNED_VALUE);
+#  endif
 # endif
 
 # ifdef RUBY19_OR_LATER
@@ -506,7 +510,11 @@ SIGNED_VALUE rb_num2long_stub(VALUE x)
 {
     return dll_rb_num2long(x);
 }
+# ifdef DYNAMIC_RUBY_VER >= 26
+VALUE rb_int2big_stub(intptr_t x)
+# else
 VALUE rb_int2big_stub(SIGNED_VALUE x)
+# endif
 {
     return dll_rb_int2big(x);
 }