diff --git a/dlls/msvcrt/except.c b/dlls/msvcrt/except.c
index f5c8b03..c7b3be9 100644
--- a/dlls/msvcrt/except.c
+++ b/dlls/msvcrt/except.c
@@ -189,11 +189,15 @@ void msvcrt_free_signals(void)
  */
 MSVCRT___sighandler_t CDECL MSVCRT_signal(int sig, MSVCRT___sighandler_t func)
 {
-    MSVCRT___sighandler_t ret = MSVCRT_SIG_ERR;
+    MSVCRT___sighandler_t ret;
 
     TRACE("(%d, %p)\n", sig, func);
 
-    if (func == MSVCRT_SIG_ERR) return MSVCRT_SIG_ERR;
+    if (func == MSVCRT_SIG_ERR)
+    {
+        *MSVCRT__errno() = MSVCRT_EINVAL;
+        return MSVCRT_SIG_ERR;
+    }
 
     switch (sig)
     {
@@ -211,6 +215,7 @@ MSVCRT___sighandler_t CDECL MSVCRT_signal(int sig, MSVCRT___sighandler_t func)
         sighandlers[sig] = func;
         break;
     default:
+        *MSVCRT__errno() = MSVCRT_EINVAL;
         ret = MSVCRT_SIG_ERR;
     }
     return ret;