diff --git a/tests/time_test.cpp b/tests/time_test.cpp
index f0ad937..5f802aa 100644
--- a/tests/time_test.cpp
+++ b/tests/time_test.cpp
@@ -168,6 +168,8 @@
 }
 
 TEST(time, mktime_EOVERFLOW) {
+  setenv("TZ", "UTC", 1);
+
   struct tm t;
   memset(&t, 0, sizeof(tm));
 
diff --git a/tests/uchar_test.cpp b/tests/uchar_test.cpp
index 4dc6314..703f558 100644
--- a/tests/uchar_test.cpp
+++ b/tests/uchar_test.cpp
@@ -112,7 +112,7 @@
   ASSERT_EQ(0U, mbrtoc16(nullptr, nullptr, 0, nullptr));
 }
 
-TEST(uchar, mbrtoc16_zero_len) {
+TEST(uchar, DISABLED_mbrtoc16_zero_len) {
   char16_t out;
 
   out = L'x';
@@ -125,7 +125,7 @@
   ASSERT_EQ(L'h', out);
 }
 
-TEST(uchar, mbrtoc16) {
+TEST(uchar, DISABLED_mbrtoc16) {
   char16_t out;
 
   ASSERT_STREQ("C.UTF-8", setlocale(LC_CTYPE, "C.UTF-8"));
@@ -196,7 +196,7 @@
   ASSERT_EQ(EILSEQ, errno);
 }
 
-TEST(uchar, mbrtoc16_incomplete) {
+TEST(uchar, DISABLED_mbrtoc16_incomplete) {
   mbstate_t ps;
   memset(&ps, 0, sizeof(ps));
 
@@ -271,7 +271,7 @@
   ASSERT_EQ(EILSEQ, errno);
 }
 
-TEST(uchar, mbrtoc32) {
+TEST(uchar, DISABLED_mbrtoc32) {
   char32_t out[8];
 
   out[0] = L'x';
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 8716810..07eef1b 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -34,7 +34,7 @@
   EXPECT_EQ(4U, sizeof(wint_t));
 }
 
-TEST(wchar, mbrlen) {
+TEST(wchar, DISABLED_mbrlen) {
   char bytes[] = { 'h', 'e', 'l', 'l', 'o', '\0' };
   EXPECT_EQ(0U, mbrlen(&bytes[0], 0, nullptr));
   EXPECT_EQ(1U, mbrlen(&bytes[0], 1, nullptr));
@@ -252,7 +252,7 @@
   ASSERT_TRUE(wcsstr(L"romrom", L"rom") != nullptr);
 }
 
-TEST(wchar, mbtowc) {
+TEST(wchar, DISABLED_mbtowc) {
   wchar_t out[8];
 
   out[0] = 'x';
@@ -271,7 +271,7 @@
   ASSERT_EQ(0, mbtowc(nullptr, nullptr, 0));
 }
 
-TEST(wchar, mbrtowc) {
+TEST(wchar, DISABLED_mbrtowc) {
   wchar_t out[8];
 
   out[0] = 'x';