diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 837de5b5..4b1854a3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -140,7 +140,7 @@ jobs:
           make cxxtest
 
       - name: test
-        if: ${{ matrix.config.configType != 'examples' && matrix.config.configType != 'tcc' }}
+        if: ${{ matrix.config.configType != 'examples' }}
         run: |
           make test
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index db4912d8..9fe136f3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -289,14 +289,7 @@ endif()
 # Test262 runner
 #
 
-if(EMSCRIPTEN
-OR CMAKE_C_COMPILER_ID STREQUAL "TinyCC"
-OR (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 5))
-    # Empty. run-test262 uses pthreads, sorry Windows users.
-    # tcc and gcc 4.8 don't understand _Thread_local, whereas I
-    # don't understand why people still use 4.8 in this day and age
-    # but hey, here we are.
-else()
+if(NOT EMSCRIPTEN)
     add_executable(run-test262
         run-test262.c
     )
diff --git a/run-test262.c b/run-test262.c
index 5000f480..c63b9102 100644
--- a/run-test262.c
+++ b/run-test262.c
@@ -50,6 +50,17 @@ typedef pthread_t js_thread_t;
 
 #define CMD_NAME "run-test262"
 
+typedef struct {
+    js_mutex_t agent_mutex;
+    js_cond_t agent_cond;
+    /* list of Test262Agent.link */
+    struct list_head agent_list;
+    js_mutex_t report_mutex;
+    /* list of AgentReport.link */
+    struct list_head report_list;
+    int async_done;
+} ThreadLocalStorage;
+
 typedef struct namelist_t {
     char **array;
     int count;
@@ -97,7 +108,6 @@ int start_index, stop_index;
 int test_excluded;
 _Atomic int test_count, test_failed, test_skipped;
 _Atomic int new_errors, changed_errors, fixed_errors;
-_Thread_local int async_done;
 
 void warning(const char *, ...) __attribute__((__format__(__printf__, 1, 2)));
 void fatal(int, const char *, ...) __attribute__((__format__(__printf__, 2, 3)));
@@ -443,6 +453,7 @@ static void enumerate_tests(const char *path)
 static JSValue js_print_262(JSContext *ctx, JSValue this_val,
                         int argc, JSValue *argv)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     int i;
     const char *str;
 
@@ -451,9 +462,9 @@ static JSValue js_print_262(JSContext *ctx, JSValue this_val,
         if (!str)
             return JS_EXCEPTION;
         if (!strcmp(str, "Test262:AsyncTestComplete")) {
-            async_done++;
+            tls->async_done++;
         } else if (strstart(str, "Test262:AsyncTestFailure", NULL)) {
-            async_done = 2; /* force an error */
+            tls->async_done = 2; /* force an error */
         }
         if (outfile) {
             if (i != 0)
@@ -552,16 +563,6 @@ static long cpu_count(void)
 #endif
 }
 
-typedef struct {
-    js_mutex_t agent_mutex;
-    js_cond_t agent_cond;
-    /* list of Test262Agent.link */
-    struct list_head agent_list;
-    js_mutex_t report_mutex;
-    /* list of AgentReport.link */
-    struct list_head report_list;
-} ThreadLocalStorage;
-
 static void init_thread_local_storage(ThreadLocalStorage *p)
 {
     js_mutex_init(&p->agent_mutex);
@@ -569,11 +570,9 @@ static void init_thread_local_storage(ThreadLocalStorage *p)
     init_list_head(&p->agent_list);
     js_mutex_init(&p->report_mutex);
     init_list_head(&p->report_list);
+    p->async_done = 0;
 }
 
-// points to parent thread's TLS in agent threads
-static _Thread_local ThreadLocalStorage *tls;
-
 typedef struct {
     struct list_head link;
     js_thread_t tid;
@@ -597,17 +596,20 @@ static void add_helpers(JSContext *ctx);
 
 static void *agent_start(void *arg)
 {
-    Test262Agent *agent = arg;
+    ThreadLocalStorage *tls;
+    Test262Agent *agent;
     JSRuntime *rt;
     JSContext *ctx;
     JSValue ret_val;
     int ret;
 
+    agent = arg;
     tls = agent->tls; // shares thread-local storage with parent thread
     rt = JS_NewRuntime();
     if (rt == NULL) {
         fatal(1, "JS_NewRuntime failure");
     }
+    JS_SetRuntimeOpaque(rt, tls);
     ctx = JS_NewContext(rt);
     if (ctx == NULL) {
         JS_FreeRuntime(rt);
@@ -674,6 +676,7 @@ static void *agent_start(void *arg)
 static JSValue js_agent_start(JSContext *ctx, JSValue this_val,
                               int argc, JSValue *argv)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     const char *script;
     Test262Agent *agent;
 
@@ -697,6 +700,7 @@ static JSValue js_agent_start(JSContext *ctx, JSValue this_val,
 
 static void js_agent_free(JSContext *ctx)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     struct list_head *el, *el1;
     Test262Agent *agent;
 
@@ -719,7 +723,7 @@ static JSValue js_agent_leaving(JSContext *ctx, JSValue this_val,
     return JS_UNDEFINED;
 }
 
-static BOOL is_broadcast_pending(void)
+static BOOL is_broadcast_pending(ThreadLocalStorage *tls)
 {
     struct list_head *el;
     Test262Agent *agent;
@@ -734,6 +738,7 @@ static BOOL is_broadcast_pending(void)
 static JSValue js_agent_broadcast(JSContext *ctx, JSValue this_val,
                                   int argc, JSValue *argv)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     JSValue sab = argv[0];
     struct list_head *el;
     Test262Agent *agent;
@@ -765,7 +770,7 @@ static JSValue js_agent_broadcast(JSContext *ctx, JSValue this_val,
     }
     js_cond_broadcast(&tls->agent_cond);
 
-    while (is_broadcast_pending()) {
+    while (is_broadcast_pending(tls)) {
         js_cond_wait(&tls->agent_cond, &tls->agent_mutex);
     }
     js_mutex_unlock(&tls->agent_mutex);
@@ -819,6 +824,7 @@ static JSValue js_agent_monotonicNow(JSContext *ctx, JSValue this_val,
 static JSValue js_agent_getReport(JSContext *ctx, JSValue this_val,
                                   int argc, JSValue *argv)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     AgentReport *rep;
     JSValue ret;
 
@@ -843,6 +849,7 @@ static JSValue js_agent_getReport(JSContext *ctx, JSValue this_val,
 static JSValue js_agent_report(JSContext *ctx, JSValue this_val,
                                int argc, JSValue *argv)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     const char *str;
     AgentReport *rep;
 
@@ -1338,6 +1345,7 @@ static int eval_buf(JSContext *ctx, const char *buf, size_t buf_len,
                     const char *error_type, int eval_flags, int is_async,
                     int *msec)
 {
+    ThreadLocalStorage *tls = JS_GetRuntimeOpaque(JS_GetRuntime(ctx));
     JSValue res_val, exception_val;
     int ret, error_line, pos, pos_line;
     BOOL is_error, has_error_line, ret_promise;
@@ -1352,7 +1360,7 @@ static int eval_buf(JSContext *ctx, const char *buf, size_t buf_len,
 
     /* a module evaluation returns a promise */
     ret_promise = ((eval_flags & JS_EVAL_TYPE_MODULE) != 0);
-    async_done = 0; /* counter of "Test262:AsyncTestComplete" messages */
+    tls->async_done = 0; /* counter of "Test262:AsyncTestComplete" messages */
 
     start = get_clock_ms();
     res_val = JS_Eval(ctx, buf, buf_len, filename, eval_flags);
@@ -1373,7 +1381,7 @@ static int eval_buf(JSContext *ctx, const char *buf, size_t buf_len,
             } else if (ret == 0) {
                 if (is_async) {
                     /* test if the test called $DONE() once */
-                    if (async_done != 1) {
+                    if (tls->async_done != 1) {
                         res_val = JS_ThrowTypeError(ctx, "$DONE() not called");
                     } else {
                         res_val = JS_UNDEFINED;
@@ -1721,10 +1729,10 @@ JSContext *JS_NewCustomContext(JSRuntime *rt)
     return ctx;
 }
 
-int run_test_buf(const char *filename, char *harness, namelist_t *ip,
-                 char *buf, size_t buf_len, const char* error_type,
-                 int eval_flags, BOOL is_negative, BOOL is_async,
-                 BOOL can_block, int *msec)
+int run_test_buf(ThreadLocalStorage *tls, const char *filename, char *harness,
+                 namelist_t *ip, char *buf, size_t buf_len,
+                 const char* error_type, int eval_flags, BOOL is_negative,
+                 BOOL is_async, BOOL can_block, int *msec)
 {
     JSRuntime *rt;
     JSContext *ctx;
@@ -1734,6 +1742,7 @@ int run_test_buf(const char *filename, char *harness, namelist_t *ip,
     if (rt == NULL) {
         fatal(1, "JS_NewRuntime failure");
     }
+    JS_SetRuntimeOpaque(rt, tls);
     js_std_init_handlers(rt);
     ctx = JS_NewCustomContext(rt);
     if (ctx == NULL) {
@@ -1782,7 +1791,7 @@ int run_test_buf(const char *filename, char *harness, namelist_t *ip,
     return ret;
 }
 
-int run_test(const char *filename, int *msec)
+int run_test(ThreadLocalStorage *tls, const char *filename, int *msec)
 {
     char harnessbuf[1024];
     char *harness;
@@ -1943,12 +1952,12 @@ int run_test(const char *filename, int *msec)
         }
         ret = 0;
         if (use_nostrict) {
-            ret = run_test_buf(filename, harness, ip, buf, buf_len,
+            ret = run_test_buf(tls, filename, harness, ip, buf, buf_len,
                                error_type, eval_flags, is_negative, is_async,
                                can_block, msec);
         }
         if (use_strict) {
-            ret |= run_test_buf(filename, harness, ip, buf, buf_len,
+            ret |= run_test_buf(tls, filename, harness, ip, buf, buf_len,
                                 error_type, eval_flags | JS_EVAL_FLAG_STRICT,
                                 is_negative, is_async, can_block, msec);
         }
@@ -1961,7 +1970,8 @@ int run_test(const char *filename, int *msec)
 }
 
 /* run a test when called by test262-harness+eshost */
-int run_test262_harness_test(const char *filename, BOOL is_module)
+int run_test262_harness_test(ThreadLocalStorage *tls, const char *filename,
+                             BOOL is_module)
 {
     JSRuntime *rt;
     JSContext *ctx;
@@ -1977,6 +1987,7 @@ int run_test262_harness_test(const char *filename, BOOL is_module)
     if (rt == NULL) {
         fatal(1, "JS_NewRuntime failure");
     }
+    JS_SetRuntimeOpaque(rt, tls);
     ctx = JS_NewContext(rt);
     if (ctx == NULL) {
         JS_FreeRuntime(rt);
@@ -2072,10 +2083,10 @@ int include_exclude_or_skip(int i) // naming is hard...
 
 void *run_test_dir_list(void *arg)
 {
+    ThreadLocalStorage tls_s, *tls = &tls_s;
     const char *p;
     int i, msec;
 
-    tls = &(ThreadLocalStorage){};
     init_thread_local_storage(tls);
 
     for (i = (uintptr_t)arg; i < test_list.count; i += nthreads) {
@@ -2083,7 +2094,7 @@ void *run_test_dir_list(void *arg)
             continue;
         p = test_list.array[i];
         msec = 0;
-        run_test(p, &msec);
+        run_test(tls, p, &msec);
         if (verbose > 1 || (slow_test_threshold && msec >= slow_test_threshold))
             fprintf(stderr, "%s (%d ms)\n", p, msec);
     }
@@ -2124,6 +2135,7 @@ char *get_opt_arg(const char *option, char *arg)
 
 int main(int argc, char **argv)
 {
+    ThreadLocalStorage tls_s, *tls = &tls_s;
     int i, optind;
     BOOL is_dir_list;
     BOOL only_check_errors = FALSE;
@@ -2134,7 +2146,6 @@ int main(int argc, char **argv)
 
     js_std_set_worker_new_context_func(JS_NewCustomContext);
 
-    tls = &(ThreadLocalStorage){};
     init_thread_local_storage(tls);
     js_mutex_init(&stats_mutex);
 
@@ -2209,7 +2220,7 @@ int main(int argc, char **argv)
         help();
 
     if (is_test262_harness) {
-        return run_test262_harness_test(argv[optind], is_module);
+        return run_test262_harness_test(tls, argv[optind], is_module);
     }
 
     nthreads = max_int(nthreads, 1);
@@ -2276,7 +2287,7 @@ int main(int argc, char **argv)
     } else {
         while (optind < argc) {
             int msec = 0;
-            run_test(argv[optind++], &msec);
+            run_test(tls, argv[optind++], &msec);
         }
     }