--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -54,6 +54,9 @@
 #endif
 
 #include <ruby.h>
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+# include <ruby/encoding.h>
+#endif
 
 #undef EXTERN
 #undef _
@@ -65,6 +68,28 @@
 # define __OPENTRANSPORTPROVIDERS__
 #endif
 
+/*
+ * Backward compatiblity for Ruby 1.8 and earlier.
+ * Ruby 1.9 does not provide STR2CSTR, instead StringValuePtr is provided.
+ * Ruby 1.9 does not provide RXXX(s)->len and RXXX(s)->ptr, instead
+ * RXXX_LEN(s) and RXXX_PTR(s) are provided.
+ */
+#ifndef StringValuePtr
+# define StringValuePtr(s) STR2CSTR(s)
+#endif
+#ifndef RARRAY_LEN
+# define RARRAY_LEN(s) RARRAY(s)->len
+#endif
+#ifndef RARRAY_PTR
+# define RARRAY_PTR(s) RARRAY(s)->ptr
+#endif
+#ifndef RSTRING_LEN
+# define RSTRING_LEN(s) RSTRING(s)->len
+#endif
+#ifndef RSTRING_PTR
+# define RSTRING_PTR(s) RSTRING(s)->ptr
+#endif
+
 #include "vim.h"
 #include "version.h"
 
@@ -134,7 +159,11 @@ static void ruby_vim_init(void);
 #define rb_str_concat			dll_rb_str_concat
 #define rb_str_new			dll_rb_str_new
 #define rb_str_new2			dll_rb_str_new2
-#define ruby_errinfo			(*dll_ruby_errinfo)
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+# define rb_errinfo			dll_rb_errinfo
+#else
+# define ruby_errinfo			(*dll_ruby_errinfo)
+#endif
 #define ruby_init			dll_ruby_init
 #define ruby_init_loadpath		dll_ruby_init_loadpath
 #define NtInitialize			dll_NtInitialize
@@ -142,6 +171,14 @@ static void ruby_vim_init(void);
 # define rb_w32_snprintf		dll_rb_w32_snprintf
 #endif
 
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+# define ruby_script			dll_ruby_script
+# define rb_enc_find_index		dll_rb_enc_find_index
+# define rb_enc_find			dll_rb_enc_find
+# define rb_enc_str_new			dll_rb_enc_str_new
+# define rb_sprintf			dll_rb_sprintf
+#endif
+
 /*
  * Pointers for dynamic link
  */
@@ -189,7 +226,11 @@ static VALUE (*dll_rb_str_cat) (VALUE, c
 static VALUE (*dll_rb_str_concat) (VALUE, VALUE);
 static VALUE (*dll_rb_str_new) (const char*, long);
 static VALUE (*dll_rb_str_new2) (const char*);
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+static VALUE (*dll_rb_errinfo) (void);
+#else
 static VALUE *dll_ruby_errinfo;
+#endif
 static void (*dll_ruby_init) (void);
 static void (*dll_ruby_init_loadpath) (void);
 static void (*dll_NtInitialize) (int*, char***);
@@ -197,6 +238,14 @@ static void (*dll_NtInitialize) (int*, c
 static int (*dll_rb_w32_snprintf)(char*, size_t, const char*, ...);
 #endif
 
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+static void (*dll_ruby_script) (const char*);
+static int (*dll_rb_enc_find_index) (const char*);
+static rb_encoding* (*dll_rb_enc_find) (const char*);
+static VALUE (*dll_rb_enc_str_new) (const char*, long, rb_encoding*);
+static VALUE (*dll_rb_sprintf) (const char*, ...);
+#endif
+
 static HINSTANCE hinstRuby = 0; /* Instance of ruby.dll */
 
 /*
@@ -252,13 +301,24 @@ static struct
     {"rb_str_concat", (RUBY_PROC*)&dll_rb_str_concat},
     {"rb_str_new", (RUBY_PROC*)&dll_rb_str_new},
     {"rb_str_new2", (RUBY_PROC*)&dll_rb_str_new2},
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+    {"rb_errinfo", (RUBY_PROC*)&dll_rb_errinfo},
+#else
     {"ruby_errinfo", (RUBY_PROC*)&dll_ruby_errinfo},
+#endif
     {"ruby_init", (RUBY_PROC*)&dll_ruby_init},
     {"ruby_init_loadpath", (RUBY_PROC*)&dll_ruby_init_loadpath},
     {"NtInitialize", (RUBY_PROC*)&dll_NtInitialize},
 #if defined(DYNAMIC_RUBY_VER) && DYNAMIC_RUBY_VER >= 18
     {"rb_w32_snprintf", (RUBY_PROC*)&dll_rb_w32_snprintf},
 #endif
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+    {"ruby_script", (RUBY_PROC*)&dll_ruby_script},
+    {"rb_enc_find_index", (RUBY_PROC*)&dll_rb_enc_find_index},
+    {"rb_enc_find", (RUBY_PROC*)&dll_rb_enc_find},
+    {"rb_enc_str_new", (RUBY_PROC*)&dll_rb_enc_str_new},
+    {"rb_sprintf", (RUBY_PROC*)&dll_rb_sprintf},
+#endif
     {"", NULL},
 };
 
@@ -348,6 +408,58 @@ void ex_ruby(exarg_T *eap)
     vim_free(script);
 }
 
+/*
+ *  In Ruby 1.9 or later, ruby String object has encoding.
+ *  conversion buffer string of vim to ruby String object using
+ *  VIM encoding option.
+ */
+    static VALUE
+vim_str2rb_enc_str(const char *s)
+{
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+    int isnum;
+    long lval;
+    char_u *sval;
+    rb_encoding *enc;
+
+    isnum = get_option_value((char_u *)"enc", &lval, &sval, 0);
+    if (isnum == 0)
+    {
+	enc = rb_enc_find((char *)sval);
+	vim_free(sval);
+	if (enc) {
+	    return rb_enc_str_new(s, strlen(s), enc);
+	}
+    }
+#endif
+    return rb_str_new2(s);
+}
+
+    static VALUE
+eval_enc_string_protect(const char *str, int *state)
+{
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+    int isnum;
+    long lval;
+    char_u *sval;
+    rb_encoding *enc;
+    VALUE v;
+
+    isnum = get_option_value((char_u *)"enc", &lval, &sval, 0);
+    if (isnum == 0)
+    {
+	enc = rb_enc_find((char *)sval);
+	vim_free(sval);
+	if (enc)
+	{
+	    v = rb_sprintf("#-*- coding:%s -*-\n%s", rb_enc_name(enc), str);
+	    return rb_eval_string_protect(StringValuePtr(v), state);
+	}
+    }
+#endif
+    return rb_eval_string_protect(str, state);
+}
+
 void ex_rubydo(exarg_T *eap)
 {
     int state;
@@ -360,9 +472,9 @@ void ex_rubydo(exarg_T *eap)
 	for (i = eap->line1; i <= eap->line2; i++) {
 	    VALUE line, oldline;
 
-	    line = oldline = rb_str_new2((char *)ml_get(i));
+	    line = oldline = vim_str2rb_enc_str((char *)ml_get(i));
 	    rb_lastline_set(line);
-	    rb_eval_string_protect((char *) eap->arg, &state);
+	    eval_enc_string_protect((char *) eap->arg, &state);
 	    if (state) {
 		error_print(state);
 		break;
@@ -373,7 +485,7 @@ void ex_rubydo(exarg_T *eap)
 		    EMSG(_("E265: $_ must be an instance of String"));
 		    return;
 		}
-		ml_replace(i, (char_u *) STR2CSTR(line), 1);
+		ml_replace(i, (char_u *) StringValuePtr(line), 1);
 		changed();
 #ifdef SYNTAX_HL
 		syn_changed(i); /* recompute syntax hl. for this line */
@@ -428,9 +540,18 @@ static int ensure_ruby_initialized(void)
 	    char *argv[] = {"gvim.exe"};
 	    NtInitialize(&argc, &argv);
 #endif
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+	    RUBY_INIT_STACK;
+#endif
 	    ruby_init();
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+	    ruby_script("vim-ruby");
+#endif
 	    ruby_init_loadpath();
 	    ruby_io_init();
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+	    rb_enc_find_index("encdb");
+#endif
 	    ruby_vim_init();
 	    ruby_initialized = 1;
 #ifdef DYNAMIC_RUBY
@@ -448,8 +569,10 @@ static int ensure_ruby_initialized(void)
 static void error_print(int state)
 {
 #ifndef DYNAMIC_RUBY
+#if !(defined(RUBY_VERSION) &&  RUBY_VERSION >= 19)
     RUBYEXTERN VALUE ruby_errinfo;
 #endif
+#endif
     VALUE eclass;
     VALUE einfo;
     char buff[BUFSIZ];
@@ -482,9 +605,14 @@ static void error_print(int state)
 	break;
     case TAG_RAISE:
     case TAG_FATAL:
+#if defined(RUBY_VERSION) && RUBY_VERSION >= 19
+	eclass = CLASS_OF(rb_errinfo());
+	einfo = rb_obj_as_string(rb_errinfo());
+#else
 	eclass = CLASS_OF(ruby_errinfo);
 	einfo = rb_obj_as_string(ruby_errinfo);
-	if (eclass == rb_eRuntimeError && RSTRING(einfo)->len == 0) {
+#endif
+	if (eclass == rb_eRuntimeError && RSTRING_LEN(einfo) == 0) {
 	    EMSG(_("E272: unhandled exception"));
 	}
 	else {
@@ -493,7 +621,7 @@ static void error_print(int state)
 
 	    epath = rb_class_path(eclass);
 	    vim_snprintf(buff, BUFSIZ, "%s: %s",
-		     RSTRING(epath)->ptr, RSTRING(einfo)->ptr);
+		     RSTRING_PTR(epath), RSTRING_PTR(einfo));
 	    p = strchr(buff, '\n');
 	    if (p) *p = '\0';
 	    EMSG(buff);
@@ -511,8 +639,8 @@ static VALUE vim_message(VALUE self UNUS
     char *buff, *p;
 
     str = rb_obj_as_string(str);
-    buff = ALLOCA_N(char, RSTRING(str)->len);
-    strcpy(buff, RSTRING(str)->ptr);
+    buff = ALLOCA_N(char, RSTRING_LEN(str));
+    strcpy(buff, RSTRING_PTR(str));
     p = strchr(buff, '\n');
     if (p) *p = '\0';
     MSG(buff);
@@ -521,21 +649,21 @@ static VALUE vim_message(VALUE self UNUS
 
 static VALUE vim_set_option(VALUE self UNUSED, VALUE str)
 {
-    do_set((char_u *)STR2CSTR(str), 0);
+    do_set((char_u *)StringValuePtr(str), 0);
     update_screen(NOT_VALID);
     return Qnil;
 }
 
 static VALUE vim_command(VALUE self UNUSED, VALUE str)
 {
-    do_cmdline_cmd((char_u *)STR2CSTR(str));
+    do_cmdline_cmd((char_u *)StringValuePtr(str));
     return Qnil;
 }
 
 static VALUE vim_evaluate(VALUE self UNUSED, VALUE str)
 {
 #ifdef FEAT_EVAL
-    char_u *value = eval_to_string((char_u *)STR2CSTR(str), NULL, TRUE);
+    char_u *value = eval_to_string((char_u *)StringValuePtr(str), NULL, TRUE);
 
     if (value != NULL)
     {
@@ -640,9 +768,9 @@ static VALUE get_buffer_line(buf_T *buf,
     if (n > 0 && n <= buf->b_ml.ml_line_count)
     {
 	char *line = (char *)ml_get_buf(buf, n, FALSE);
-	return line ? rb_str_new2(line) : Qnil;
+	return line ? vim_str2rb_enc_str(line) : Qnil;
     }
-    rb_raise(rb_eIndexError, "index %d out of buffer", n);
+    rb_raise(rb_eIndexError, "line number %ld out of range", (long)n);
 #ifndef __GNUC__
     return Qnil; /* For stop warning */
 #endif
@@ -659,7 +787,7 @@ static VALUE buffer_aref(VALUE self, VAL
 
 static VALUE set_buffer_line(buf_T *buf, linenr_T n, VALUE str)
 {
-    char	*line = STR2CSTR(str);
+    char	*line = StringValuePtr(str);
     aco_save_T	aco;
 
     if (n > 0 && n <= buf->b_ml.ml_line_count && line != NULL)
@@ -683,7 +811,7 @@ static VALUE set_buffer_line(buf_T *buf,
     }
     else
     {
-	rb_raise(rb_eIndexError, "index %d out of buffer", n);
+	rb_raise(rb_eIndexError, "line number %ld out of range", (long)n);
 #ifndef __GNUC__
 	return Qnil; /* For stop warning */
 #endif
@@ -729,7 +857,7 @@ static VALUE buffer_delete(VALUE self, V
     }
     else
     {
-	rb_raise(rb_eIndexError, "index %d out of buffer", n);
+	rb_raise(rb_eIndexError, "line number %ld out of range", n);
     }
     return Qnil;
 }
@@ -737,11 +865,14 @@ static VALUE buffer_delete(VALUE self, V
 static VALUE buffer_append(VALUE self, VALUE num, VALUE str)
 {
     buf_T	*buf = get_buf(self);
-    char	*line = STR2CSTR(str);
+    char	*line = StringValuePtr(str);
     long	n = NUM2LONG(num);
     aco_save_T	aco;
 
-    if (n >= 0 && n <= buf->b_ml.ml_line_count && line != NULL)
+    if (line != NULL) {
+	rb_raise(rb_eIndexError, "NULL line");
+    }
+    else if (n >= 0 && n <= buf->b_ml.ml_line_count)
     {
 	/* set curwin/curbuf for "buf" and save some things */
 	aucmd_prepbuf(&aco, buf);
@@ -763,7 +894,7 @@ static VALUE buffer_append(VALUE self, V
 	update_curbuf(NOT_VALID);
     }
     else {
-	rb_raise(rb_eIndexError, "index %d out of buffer", n);
+	rb_raise(rb_eIndexError, "line number %ld out of range", n);
     }
     return str;
 }
@@ -904,10 +1035,10 @@ static VALUE window_set_cursor(VALUE sel
     win_T *win = get_win(self);
 
     Check_Type(pos, T_ARRAY);
-    if (RARRAY(pos)->len != 2)
+    if (RARRAY_LEN(pos) != 2)
 	rb_raise(rb_eArgError, "array length must be 2");
-    lnum = RARRAY(pos)->ptr[0];
-    col = RARRAY(pos)->ptr[1];
+    lnum = RARRAY_PTR(pos)[0];
+    col = RARRAY_PTR(pos)[1];
     win->w_cursor.lnum = NUM2LONG(lnum);
     win->w_cursor.col = NUM2UINT(col);
     check_cursor();		    /* put cursor on an existing line */
@@ -924,7 +1055,7 @@ static VALUE f_p(int argc, VALUE *argv, 
 	if (i > 0) rb_str_cat(str, ", ", 2);
 	rb_str_concat(str, rb_inspect(argv[i]));
     }
-    MSG(RSTRING(str)->ptr);
+    MSG(RSTRING_PTR(str));
     return Qnil;
 }