diff --git a/ChangeLog b/ChangeLog
index 43642d7252..fd8b2b7218 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Fri Mar 23 13:19:20 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* bignum.c (rb_str_to_inum): must be ASCII compatible encoding as
+	  well as String#hex and String#oct.  [ruby-core:43566][Bug #6192]
+
+	* string.c (rb_must_asciicompat): check if ASCII compatible.
+
 Thu Mar 22 23:14:36 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* transcode.c (str_encode_bang, encoded_dup): if nothing was
diff --git a/bignum.c b/bignum.c
index fae29652b6..678a65bba7 100644
--- a/bignum.c
+++ b/bignum.c
@@ -775,6 +775,7 @@ rb_str_to_inum(VALUE str, int base, int badcheck)
     VALUE ret;
 
     StringValue(str);
+    rb_must_asciicompat(str);
     if (badcheck) {
 	s = StringValueCStr(str);
     }
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index e07f7fd781..61ed85fcdb 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -707,6 +707,7 @@ VALUE rb_str_buf_cat2(VALUE, const char*);
 VALUE rb_str_buf_cat_ascii(VALUE, const char*);
 VALUE rb_obj_as_string(VALUE);
 VALUE rb_check_string_type(VALUE);
+void rb_must_asciicompat(VALUE);
 VALUE rb_str_dup(VALUE);
 VALUE rb_str_resurrect(VALUE str);
 VALUE rb_str_locktmp(VALUE);
diff --git a/string.c b/string.c
index d06a99636e..7fd2d94e59 100644
--- a/string.c
+++ b/string.c
@@ -1409,6 +1409,15 @@ rb_str_associated(VALUE str)
     return Qfalse;
 }
 
+void
+rb_must_asciicompat(VALUE str)
+{
+    rb_encoding *enc = rb_enc_get(str);
+    if (!rb_enc_asciicompat(enc)) {
+	rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
+    }
+}
+
 VALUE
 rb_string_value(volatile VALUE *ptr)
 {
@@ -6722,11 +6731,6 @@ rb_str_scan(VALUE str, VALUE pat)
 static VALUE
 rb_str_hex(VALUE str)
 {
-    rb_encoding *enc = rb_enc_get(str);
-
-    if (!rb_enc_asciicompat(enc)) {
-	rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
-    }
     return rb_str_to_inum(str, 16, FALSE);
 }
 
@@ -6748,11 +6752,6 @@ rb_str_hex(VALUE str)
 static VALUE
 rb_str_oct(VALUE str)
 {
-    rb_encoding *enc = rb_enc_get(str);
-
-    if (!rb_enc_asciicompat(enc)) {
-	rb_raise(rb_eEncCompatError, "ASCII incompatible encoding: %s", rb_enc_name(enc));
-    }
     return rb_str_to_inum(str, -8, FALSE);
 }
 
diff --git a/test/ruby/test_integer.rb b/test/ruby/test_integer.rb
index 7f8212ebf0..3f4add7f15 100644
--- a/test/ruby/test_integer.rb
+++ b/test/ruby/test_integer.rb
@@ -90,6 +90,13 @@ class TestInteger < Test::Unit::TestCase
 
     assert_equal(2 ** 50, Integer(2.0 ** 50))
     assert_raise(TypeError) { Integer(nil) }
+
+    bug6192 = '[ruby-core:43566]'
+    assert_raise(Encoding::CompatibilityError, bug6192) {Integer("0".encode("utf-16be"))}
+    assert_raise(Encoding::CompatibilityError, bug6192) {Integer("0".encode("utf-16le"))}
+    assert_raise(Encoding::CompatibilityError, bug6192) {Integer("0".encode("utf-32be"))}
+    assert_raise(Encoding::CompatibilityError, bug6192) {Integer("0".encode("utf-32le"))}
+    assert_raise(Encoding::CompatibilityError, bug6192) {Integer("0".encode("iso-2022-jp"))}
   end
 
   def test_int_p
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 622ba9ea63..f8336679b5 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -1465,6 +1465,13 @@ class TestString < Test::Unit::TestCase
     assert_equal(0x4000000000000000, "4611686018427387904".to_i(10))
     assert_equal(1, "1__2".to_i(10))
     assert_equal(1, "1_z".to_i(10))
+
+    bug6192 = '[ruby-core:43566]'
+    assert_raise(Encoding::CompatibilityError, bug6192) {"0".encode("utf-16be").to_i}
+    assert_raise(Encoding::CompatibilityError, bug6192) {"0".encode("utf-16le").to_i}
+    assert_raise(Encoding::CompatibilityError, bug6192) {"0".encode("utf-32be").to_i}
+    assert_raise(Encoding::CompatibilityError, bug6192) {"0".encode("utf-32le").to_i}
+    assert_raise(Encoding::CompatibilityError, bug6192) {"0".encode("iso-2022-jp").to_i}
   end
 
   def test_to_s