diff --git a/compat/mingw.c b/compat/mingw.c
index b67362558..b295e2f6a 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -841,8 +841,8 @@ struct pinfo_t {
 	struct pinfo_t *next;
 	pid_t pid;
 	HANDLE proc;
-} pinfo_t;
-struct pinfo_t *pinfo = NULL;
+};
+static struct pinfo_t *pinfo = NULL;
 CRITICAL_SECTION pinfo_cs;
 
 static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
@@ -1253,7 +1253,7 @@ static int WSAAPI getaddrinfo_stub(const char *node, const char *service,
 	else
 		sin->sin_addr.s_addr = INADDR_LOOPBACK;
 	ai->ai_addr = (struct sockaddr *)sin;
-	ai->ai_next = 0;
+	ai->ai_next = NULL;
 	return 0;
 }
 
diff --git a/compat/mingw.h b/compat/mingw.h
index 685cd2c3d..3036980ca 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -333,6 +333,13 @@ void mingw_open_html(const char *path);
 char **make_augmented_environ(const char *const *vars);
 void free_environ(char **env);
 
+/*
+ * A critical section used in the implementation of the spawn
+ * functions (mingw_spawnv[p]e()) and waitpid(). Intialised in
+ * the replacement main() macro below.
+ */
+extern CRITICAL_SECTION pinfo_cs;
+
 /*
  * A replacement of main() that ensures that argv[0] has a path
  * and that default fmode and std(in|out|err) are in binary mode