diff --git a/doc/ref/spec.md b/doc/ref/spec.md
index deb558d..0173d43 100644
--- a/doc/ref/spec.md
+++ b/doc/ref/spec.md
@@ -469,7 +469,7 @@
 "Hello, \( name )!"
 "日本語"
 "\u65e5本\U00008a9e"
-"\xff\u00FF"
+'\xff\u00FF'
 "\uD800"             // illegal: surrogate half (TODO: probably should allow)
 "\U00110000"         // illegal: invalid Unicode code point
 
@@ -486,7 +486,7 @@
 `日本語`                                 // UTF-8 input text as a raw literal
 "\u65e5\u672c\u8a9e"                    // the explicit Unicode code points
 "\U000065e5\U0000672c\U00008a9e"        // the explicit Unicode code points
-"\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e"  // the explicit UTF-8 bytes
+'\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e'  // the explicit UTF-8 bytes
 ```
 
 If the source code represents a character as two code points, such as a