diff --git a/libtcc.c b/libtcc.c
index 3094d2df..e1bfe028 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -749,7 +749,9 @@ LIBTCCAPI TCCState *tcc_new(void)
     s = tcc_mallocz(sizeof(TCCState));
     if (!s)
         return NULL;
+    WAIT_SEM();
     ++nb_states;
+    POST_SEM();
 
 #undef gnu_ext
 
@@ -958,8 +960,10 @@ LIBTCCAPI void tcc_delete(TCCState *s1)
 #endif
 
     tcc_free(s1);
+    WAIT_SEM();
     if (0 == --nb_states)
         tcc_memcheck();
+    POST_SEM();
 }
 
 LIBTCCAPI int tcc_set_output_type(TCCState *s, int output_type)
diff --git a/tests/libtcc_test_mt.c b/tests/libtcc_test_mt.c
index 266870fe..03b9f799 100644
--- a/tests/libtcc_test_mt.c
+++ b/tests/libtcc_test_mt.c
@@ -105,13 +105,15 @@ void parse_args(TCCState *s)
             else if (a[1] == 'L')
                 tcc_add_library_path(s, a+2);
             else if (a[1] == 'D') {
-                char *eq = strchr(a+2, '=');
+                char *dup = strdup(a);
+                char *eq = strchr(dup+2, '=');
                 if (eq) {
                     *eq = 0;
-                    tcc_define_symbol(s, a+2, eq+1);
+                    tcc_define_symbol(s, dup+2, eq+1);
                     *eq = '=';
                 } else
-                  tcc_define_symbol(s, a+2, NULL);
+                  tcc_define_symbol(s, dup+2, NULL);
+                free(dup);
             }
         }
     }