1 files changed, 1 insertions, 1 deletions

diff --git a/win32/process.c b/win32/process.c
index 9ad75f94f..a0e8b96e0 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -15,7 +15,7 @@ int waitpid(pid_t pid, int *status, int options)
                         return ret == -1 ? -1 : pid;
                 }
         }
-        errno = EINVAL;
+        errno = pid < 0 ? ENOSYS : EINVAL;
         return -1;
 }