diff --git a/ext/mbstring/libmbfl/filters/mbfilter_euc_tw.c b/ext/mbstring/libmbfl/filters/mbfilter_euc_tw.c
index 9b28556dee6..141a2fee7c5 100644
--- a/ext/mbstring/libmbfl/filters/mbfilter_euc_tw.c
+++ b/ext/mbstring/libmbfl/filters/mbfilter_euc_tw.c
@@ -66,7 +66,9 @@ const mbfl_encoding mbfl_encoding_euc_tw = {
 	"EUC-TW",
 	(const char *(*)[])&mbfl_encoding_euc_tw_aliases,
 	mblen_table_euctw,
-	MBFL_ENCTYPE_MBCS
+	MBFL_ENCTYPE_MBCS,
+	&vtbl_euctw_wchar,
+	&vtbl_wchar_euctw
 };
 
 const struct mbfl_identify_vtbl vtbl_identify_euctw = {
diff --git a/ext/mbstring/libmbfl/mbfl/mbfilter_8bit.c b/ext/mbstring/libmbfl/mbfl/mbfilter_8bit.c
index b38e4088064..a6a4e9f01fb 100644
--- a/ext/mbstring/libmbfl/mbfl/mbfilter_8bit.c
+++ b/ext/mbstring/libmbfl/mbfl/mbfilter_8bit.c
@@ -36,6 +36,11 @@
 
 #include "mbfilter.h"
 
+const struct mbfl_convert_vtbl vtbl_8bit_wchar;
+const struct mbfl_convert_vtbl vtbl_wchar_8bit;
+static int mbfl_filt_conv_8bit_wchar(int c, mbfl_convert_filter *filter);
+static int mbfl_filt_conv_wchar_8bit(int c, mbfl_convert_filter *filter);
+
 static const char *mbfl_encoding_8bit_aliases[] = {"binary", NULL};
 
 const mbfl_encoding mbfl_encoding_8bit = {
@@ -45,6 +50,42 @@ const mbfl_encoding mbfl_encoding_8bit = {
 	(const char *(*)[])&mbfl_encoding_8bit_aliases,
 	NULL,
 	MBFL_ENCTYPE_SBCS,
-	NULL,
-	NULL
+	&vtbl_8bit_wchar,
+	&vtbl_wchar_8bit
 };
+
+const struct mbfl_convert_vtbl vtbl_8bit_wchar = {
+	mbfl_no_encoding_8bit,
+	mbfl_no_encoding_wchar,
+	mbfl_filt_conv_common_ctor,
+	mbfl_filt_conv_common_dtor,
+	mbfl_filt_conv_8bit_wchar,
+	mbfl_filt_conv_common_flush
+};
+
+const struct mbfl_convert_vtbl vtbl_wchar_8bit = {
+	mbfl_no_encoding_wchar,
+	mbfl_no_encoding_8bit,
+	mbfl_filt_conv_common_ctor,
+	mbfl_filt_conv_common_dtor,
+	mbfl_filt_conv_wchar_8bit,
+	mbfl_filt_conv_common_flush
+};
+
+#define CK(statement) do { if ((statement) < 0) return (-1); } while (0)
+
+static int mbfl_filt_conv_8bit_wchar(int c, mbfl_convert_filter *filter)
+{
+	return (*filter->output_function)(c, filter->data);
+}
+
+static int mbfl_filt_conv_wchar_8bit(int c, mbfl_convert_filter *filter)
+{
+	if (c >= 0 && c < 0x100) {
+		CK((*filter->output_function)(c, filter->data));
+	} else {
+		CK(mbfl_filt_conv_illegal_output(c, filter));
+	}
+
+	return c;
+}
diff --git a/ext/mbstring/libmbfl/mbfl/mbfl_encoding.c b/ext/mbstring/libmbfl/mbfl/mbfl_encoding.c
index d8049617014..be861629d0e 100644
--- a/ext/mbstring/libmbfl/mbfl/mbfl_encoding.c
+++ b/ext/mbstring/libmbfl/mbfl/mbfl_encoding.c
@@ -114,22 +114,8 @@
 #endif
 
 
-static const char *mbfl_encoding_auto_aliases[] = {"unknown", NULL};
-
-static const mbfl_encoding mbfl_encoding_auto = {
-	mbfl_no_encoding_auto,
-	"auto",
-	NULL,
-	(const char *(*)[])&mbfl_encoding_auto_aliases,
-	NULL,
-	0,
-	NULL,
-	NULL
-};
-
 static const mbfl_encoding *mbfl_encoding_ptr_list[] = {
 	&mbfl_encoding_pass,
-	&mbfl_encoding_auto,
 	&mbfl_encoding_wchar,
 	&mbfl_encoding_byte2be,
 	&mbfl_encoding_byte2le,
diff --git a/ext/mbstring/libmbfl/mbfl/mbfl_encoding.h b/ext/mbstring/libmbfl/mbfl/mbfl_encoding.h
index 2952977fd88..c3a9c0affc7 100644
--- a/ext/mbstring/libmbfl/mbfl/mbfl_encoding.h
+++ b/ext/mbstring/libmbfl/mbfl/mbfl_encoding.h
@@ -36,7 +36,6 @@
 enum mbfl_no_encoding {
 	mbfl_no_encoding_invalid = -1,
 	mbfl_no_encoding_pass,
-	mbfl_no_encoding_auto,
 	mbfl_no_encoding_wchar,
 	mbfl_no_encoding_byte2be,
 	mbfl_no_encoding_byte2le,
diff --git a/ext/mbstring/tests/bug77025.phpt b/ext/mbstring/tests/bug77025.phpt
new file mode 100644
index 00000000000..46416c1df18
--- /dev/null
+++ b/ext/mbstring/tests/bug77025.phpt
@@ -0,0 +1,12 @@
+--TEST--
+Bug #77025: mb_strpos throws Unknown encoding or conversion error
+--FILE--
+<?php
+
+var_dump(mb_strpos('Hello', 'e', 0, '8bit'));
+var_dump(mb_stripos('Hello', 'e', 0, '8bit'));
+
+?>
+--EXPECT--
+int(1)
+int(1)
diff --git a/ext/mbstring/tests/mb_preferred_mime_name.phpt b/ext/mbstring/tests/mb_preferred_mime_name.phpt
index 1fa73421f69..df05027c3c6 100644
--- a/ext/mbstring/tests/mb_preferred_mime_name.phpt
+++ b/ext/mbstring/tests/mb_preferred_mime_name.phpt
@@ -38,7 +38,7 @@ echo "== INVALID PARAMETER ==\n";
 var_dump(mb_preferred_mime_name('BAD_NAME'));
 
 // No preferred name
-var_dump(mb_preferred_mime_name('auto'));
+var_dump(mb_preferred_mime_name('pass'));
 ?>
 --EXPECTF--
 Shift_JIS
@@ -55,5 +55,5 @@ UCS-4
 Warning: mb_preferred_mime_name(): Unknown encoding "BAD_NAME" in %s on line %d
 bool(false)
 
-Warning: mb_preferred_mime_name(): No MIME preferred name corresponding to "auto" in %s on line %d
+Warning: mb_preferred_mime_name(): No MIME preferred name corresponding to "pass" in %s on line %d
 bool(false)