diff --git a/src/regression/regex-escaped-high-byte.c b/src/regression/regex-escaped-high-byte.c
index 7a29489..70a8d44 100644
--- a/src/regression/regex-escaped-high-byte.c
+++ b/src/regression/regex-escaped-high-byte.c
@@ -1,5 +1,6 @@
 // commit 39dfd58417ef642307d90306e1c7e50aaec5a35c 2015-03-20
 // backslash followed by high byte should be parsed as a normal sequence
+#include <locale.h>
 #include <regex.h>
 #include "test.h"
 
@@ -9,6 +10,8 @@ int main(void)
 	regex_t r;
 	int n;
 
+	setlocale(LC_CTYPE, "C.UTF-8");
+
 	// illegal sequence (not U+00FC)
 	n = regcomp(&r, "\\\xfc", 0);
 	if (n != REG_BADPAT) {