diff --git a/kernel.rb b/kernel.rb
index de20fffcf9..9cc58bc1d9 100644
--- a/kernel.rb
+++ b/kernel.rb
@@ -169,6 +169,10 @@ module Kernel
   #     Float("123.0_badstring", exception: false)  #=> nil
   #
   def Float(arg, exception: true)
-    Primitive.rb_f_float(arg, exception)
+    if Primitive.mandatory_only?
+      Primitive.rb_f_float1(arg)
+    else
+      Primitive.rb_f_float(arg, exception)
+    end
   end
 end
diff --git a/object.c b/object.c
index f98fb83936..755645b76e 100644
--- a/object.c
+++ b/object.c
@@ -3531,6 +3531,12 @@ rb_Float(VALUE val)
     return rb_convert_to_float(val, TRUE);
 }
 
+static VALUE
+rb_f_float1(rb_execution_context_t *ec, VALUE obj, VALUE arg)
+{
+    return rb_convert_to_float(arg, TRUE);
+}
+
 static VALUE
 rb_f_float(rb_execution_context_t *ec, VALUE obj, VALUE arg, VALUE opts)
 {