diff --git a/epan/except.c b/epan/except.c
index b37cbdb04b..a9bf83fb6a 100644
--- a/epan/except.c
+++ b/epan/except.c
@@ -143,7 +143,7 @@ static void (*uh_catcher_ptr)(except_t *) = unhandled_catcher;
  * the size_t issue doesn't exists here. Pheew.. */
 static void *(*allocator)(size_t) = (void *(*)(size_t)) g_malloc;
 static void (*deallocator)(void *) = g_free;
-static struct except_stacknode *stack_top;
+static WS_THREAD_LOCAL struct except_stacknode *stack_top;
 
 #define get_top() (stack_top)
 #define set_top(T) (stack_top = (T))
diff --git a/include/ws_attributes.h b/include/ws_attributes.h
index c1082d1530..f3ecf598f1 100644
--- a/include/ws_attributes.h
+++ b/include/ws_attributes.h
@@ -75,6 +75,23 @@ extern "C" {
   #define WS_RETNONNULL
 #endif
 
+/*
+ * WS_THREAD_LOCAL means "this variable should go in thread-local
+ * storage.
+ *
+ * Based on
+ *
+ *   https://en.wikipedia.org/w/index.php?title=Thread-local_storage&oldid=1064900318#C_and_C++
+ *
+ * the major UN*X C compilers support __thread and the major Windows C
+ * compilers support __declspec(thread).
+ */
+#ifdef _WIN32
+  #define WS_THREAD_LOCAL __declspec(thread)
+#else
+  #define WS_THREAD_LOCAL __thread
+#endif
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */