diff --git a/ext/mbstring/mbstring.c b/ext/mbstring/mbstring.c
index 264c6020cab..17df6036dc2 100644
--- a/ext/mbstring/mbstring.c
+++ b/ext/mbstring/mbstring.c
@@ -4953,11 +4953,9 @@ PHP_FUNCTION(mb_chr)
 /* }}} */
 
 
-static inline char* php_mb_scrub(const char* str, size_t str_len, const mbfl_encoding *enc)
+static inline char* php_mb_scrub(const char* str, size_t str_len, const mbfl_encoding *enc, size_t *ret_len)
 {
-	size_t ret_len;
-
-	return php_mb_convert_encoding_ex(str, str_len, enc, enc, &ret_len);
+	return php_mb_convert_encoding_ex(str, str_len, enc, enc, ret_len);
 }
 
 
@@ -4969,6 +4967,7 @@ PHP_FUNCTION(mb_scrub)
 	size_t str_len;
 	zend_string *enc_name = NULL;
 	char *ret;
+	size_t ret_len;
 
 	ZEND_PARSE_PARAMETERS_START(1, 2)
 		Z_PARAM_STRING(str, str_len)
@@ -4981,13 +4980,13 @@ PHP_FUNCTION(mb_scrub)
 		RETURN_FALSE;
 	}
 
-	ret = php_mb_scrub(str, str_len, enc);
+	ret = php_mb_scrub(str, str_len, enc, &ret_len);
 
 	if (ret == NULL) {
 		RETURN_FALSE;
 	}
 
-	RETVAL_STRING(ret);
+	RETVAL_STRINGL(ret, ret_len);
 	efree(ret);
 }
 /* }}} */
diff --git a/ext/mbstring/tests/bug77454.phpt b/ext/mbstring/tests/bug77454.phpt
new file mode 100644
index 00000000000..b64452c79b7
--- /dev/null
+++ b/ext/mbstring/tests/bug77454.phpt
@@ -0,0 +1,16 @@
+--TEST--
+Bug #77454: mb_scrub() silently truncates after a null byte
+--FILE--
+<?php
+$str = "before\0after";
+function test($str, $enc) {
+    echo str_replace("\0", '\0', mb_scrub($str, $enc)), "\n";
+}
+test($str, 'latin1');
+test($str, 'utf-8');
+test($str, 'ascii');
+?>
+--EXPECT--
+before\0after
+before\0after
+before\0after