diff --git a/object.c b/object.c
index b5decf0c24..5d6b6dbad1 100644
--- a/object.c
+++ b/object.c
@@ -3489,6 +3489,7 @@ rb_str_to_dbl_raise(VALUE str, int badcheck, int raise, int *error)
     VALUE v = 0;
 
     StringValue(str);
+    rb_must_asciicompat(str);
     s = RSTRING_PTR(str);
     len = RSTRING_LEN(str);
     if (s) {
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index 415d62467e..a0b9b44464 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -850,6 +850,12 @@ class TestFloat < Test::Unit::TestCase
     o = Object.new
     def o.to_f; inf = Float::INFINITY; inf/inf; end
     assert_predicate(Float(o), :nan?)
+
+    assert_raise(Encoding::CompatibilityError) {Float("0".encode("utf-16be"))}
+    assert_raise(Encoding::CompatibilityError) {Float("0".encode("utf-16le"))}
+    assert_raise(Encoding::CompatibilityError) {Float("0".encode("utf-32be"))}
+    assert_raise(Encoding::CompatibilityError) {Float("0".encode("utf-32le"))}
+    assert_raise(Encoding::CompatibilityError) {Float("0".encode("iso-2022-jp"))}
   end
 
   def test_invalid_str
diff --git a/version.h b/version.h
index 43e825a570..9be17cfcf1 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 5
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 103
+#define RUBY_PATCHLEVEL 104
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"