diff --git a/src/util/string.h b/src/util/string.h
index 7ceb838d5..4f495ed73 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -33,7 +33,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define TOSTRING(x) STRINGIFY(x)
 
 // Checks whether a byte is an inner byte for an utf-8 multibyte sequence
-#define IS_UTF8_MULTB_INNER(x) (((unsigned char)x >= 0x80) && ((unsigned char)x <= 0xc0))
+#define IS_UTF8_MULTB_INNER(x) (((unsigned char)x >= 0x80) && ((unsigned char)x < 0xc0))
 
 typedef std::map<std::string, std::string> StringMap;