diff --git a/parse.y b/parse.y
index 1074d3ae10..bfea0c76a7 100644
--- a/parse.y
+++ b/parse.y
@@ -4947,7 +4947,6 @@ ripper_dispatch_delayed_token(struct parser_params *parser, int t)
 
 #define parser_encoding_name()  (current_enc->name)
 #define parser_mbclen()  mbclen((lex_p-1),lex_pend,current_enc)
-#define parser_precise_mbclen()  rb_enc_precise_mbclen((lex_p-1),lex_pend,current_enc)
 #define is_identchar(p,e,enc) (rb_enc_isalnum((unsigned char)(*(p)),(enc)) || (*(p)) == '_' || !ISASCII(*(p)))
 #define parser_is_identchar() (!parser->eofp && is_identchar((lex_p-1),lex_pend,current_enc))
 
@@ -5018,6 +5017,17 @@ token_info_pop_gen(struct parser_params *parser, const char *token, size_t len)
     xfree(ptinfo);
 }
 
+static int
+parser_precise_mbclen(struct parser_params *parser, const char *p)
+{
+    int len = rb_enc_precise_mbclen(p, lex_pend, current_enc);
+    if (!MBCLEN_CHARFOUND_P(len)) {
+	compile_error(PARSER_ARG "invalid multibyte char (%s)", parser_encoding_name());
+	return -1;
+    }
+    return len;
+}
+
 static int
 parser_yyerror(struct parser_params *parser, const char *msg)
 {
@@ -5930,11 +5940,8 @@ dispose_string(VALUE str)
 static int
 parser_tokadd_mbchar(struct parser_params *parser, int c)
 {
-    int len = parser_precise_mbclen();
-    if (!MBCLEN_CHARFOUND_P(len)) {
-	compile_error(PARSER_ARG "invalid multibyte char (%s)", parser_encoding_name());
-	return -1;
-    }
+    int len = parser_precise_mbclen(parser, lex_p-1);
+    if (len < 0) return -1;
     tokadd(c);
     lex_p += --len;
     if (len > 0) tokcopy(len);
@@ -7426,7 +7433,8 @@ parse_qmark(struct parser_params *parser, int space_seen)
 	if (space_seen) {
 	    const char *start = lex_p - 1, *p = start;
 	    do {
-		int n = rb_enc_precise_mbclen(p, lex_pend, current_enc);
+		int n = parser_precise_mbclen(parser, p);
+		if (n < 0) return -1;
 		p += n;
 	    } while (p < lex_pend && is_identchar(p, lex_pend, current_enc));
 	    rb_warn2("`?' just followed by `%.*s' is interpreted as" \
diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index 6030dad605..4ae2fa273f 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -512,6 +512,8 @@ class TestParse < Test::Unit::TestCase
     assert_raise(SyntaxError) { eval("?\v") }
     assert_raise(SyntaxError) { eval("?\r") }
     assert_raise(SyntaxError) { eval("?\f") }
+    assert_raise(SyntaxError) { eval("?\f") }
+    assert_raise(SyntaxError) { eval(" ?a\x8a".force_encoding("utf-8")) }
     assert_equal("\u{1234}", eval("?\u{1234}"))
     assert_equal("\u{1234}", eval('?\u{1234}'))
   end