diff --git a/posix/ex.c b/posix/ex.c
index f82b2cd..d0da174 100755
--- a/posix/ex.c
+++ b/posix/ex.c
@@ -15,7 +15,7 @@
 
 
 /* Generally useful function -- what luaL_checkudata() should do */
-void *checkuserdata(lua_State *L, int idx, const char *tname)
+extern void *checkuserdata(lua_State *L, int idx, const char *tname)
 {
     void *ud;
     luaL_argcheck(L, ud = luaL_checkudata(L, idx, tname), idx, tname);
@@ -24,7 +24,7 @@ void *checkuserdata(lua_State *L, int idx, const char *tname)
 
 
 /* -- nil error */
-int push_error(lua_State *L)
+extern int push_error(lua_State *L)
 {
 	lua_pushnil(L);
 	lua_pushstring(L, strerror(errno));
@@ -163,10 +163,22 @@ static int ex_unlock(lua_State *L)
 }
 
 
-/* -- LUA_FILEHANDLE file file */
-static int make_pipe(lua_State *L, FILE *i, FILE *o)
+static int make_pipe(FILE **i, FILE **o)
 {
-	FILE **pf;
+	int fd[2];
+	if (-1 == pipe(fd))
+		return 0;
+	*i = fdopen(fd[0], "r");
+	*o = fdopen(fd[1], "w");
+	return 1;
+}
+
+/* -- in out/nil error */
+static int ex_pipe(lua_State *L)
+{
+	FILE *i, *o, **pf;
+	if (!make_pipe(&i, &o))
+		return push_error(L);
 	luaL_getmetatable(L, LUA_FILEHANDLE);
 	*(pf = lua_newuserdata(L, sizeof *pf)) = i;
 	lua_pushvalue(L, -2);
@@ -177,15 +189,6 @@ static int make_pipe(lua_State *L, FILE *i, FILE *o)
 	return 2;
 }
 
-/* -- in out/nil error */
-static int ex_pipe(lua_State *L)
-{
-	int fd[2];
-	if (-1 == pipe(fd))
-		return push_error(L);
-	return make_pipe(L, fdopen(fd[0], "r"), fdopen(fd[1], "w"));
-}
-
 
 /* filename [args-opts] -- true/nil,error */
 /* args-opts -- true/nil,error */
diff --git a/w32api/ex.c b/w32api/ex.c
index aa6cdc7..df6baa8 100755
--- a/w32api/ex.c
+++ b/w32api/ex.c
@@ -31,7 +31,7 @@ extern HANDLE get_handle(FILE *f)
 
 
 /* -- nil error */
-static int push_error(lua_State *L)
+extern int push_error(lua_State *L)
 {
 	DWORD error = GetLastError();
 	char buffer[1024];
@@ -56,12 +56,8 @@ static int ex_getenv(lua_State *L)
 	char val[1024];
 	size_t len;
 	len = GetEnvironmentVariable(nam, val, sizeof val);
-	if (sizeof val < len)
+	if (sizeof val < len || (len == 0 && GetLastError() == ERROR_ENVVAR_NOT_FOUND))
 		return push_error(L);
-	else if (len == 0) {
-		lua_pushnil(L);
-		return 1;
-	}
 	lua_pushlstring(L, val, len);
 	return 1;
 }
@@ -194,9 +190,22 @@ static int ex_unlock(lua_State *L)
 
 
 /* -- LUA_FILEHANDLE file file */
-static int make_pipe(lua_State *L, FILE *i, FILE *o)
+static int make_pipe(FILE **i, FILE **o)
+{
+	HANDLE ph[2];
+	if (0 == CreatePipe(ph+0, ph+1, 0, 0))
+		return 0;
+	*i = _fdopen(_open_osfhandle((long)ph[0], _O_RDONLY), "r");
+	*o = _fdopen(_open_osfhandle((long)ph[1], _O_WRONLY), "w");
+	return 1;
+}
+
+/* -- in out/nil error */
+static int ex_pipe(lua_State *L)
 {
-	FILE **pf;
+	FILE *i, *o, **pf;
+	if (!make_pipe(&i, &o))
+		return push_error(L);
 	luaL_getmetatable(L, LUA_FILEHANDLE);
 	*(pf = lua_newuserdata(L, sizeof *pf)) = i;
 	lua_pushvalue(L, -2);
@@ -207,17 +216,6 @@ static int make_pipe(lua_State *L, FILE *i, FILE *o)
 	return 2;
 }
 
-/* -- in out/nil error */
-static int ex_pipe(lua_State *L)
-{
-	HANDLE ph[2];
-	if (0 == CreatePipe(ph+0, ph+1, 0, 0))
-		return push_error(L);
-	return make_pipe(L,
-		 _fdopen(_open_osfhandle((long)ph[0], _O_RDONLY), "r"),
-		 _fdopen(_open_osfhandle((long)ph[1], _O_WRONLY), "w"));
-}
-
 
 /* filename [args-opts] -- true/nil,error */
 /* args-opts -- true/nil,error */
diff --git a/w32api/spawn.c b/w32api/spawn.c
index 926a4ce..9d3c96d 100755
--- a/w32api/spawn.c
+++ b/w32api/spawn.c
@@ -10,6 +10,7 @@
 
 extern void *checkuserdata(lua_State *L, int index, const char *name);
 extern HANDLE get_handle(FILE *f);
+extern int push_error(lua_State *L);
 
 static int needs_quoting(const char *s)
 {
@@ -144,8 +145,9 @@ int process_wait(lua_State *L)
 	struct process *p = checkuserdata(L, 1, PROCESS_HANDLE);
 	if (p->status == -1) {
 		DWORD exitcode;
-		WaitForSingleObject(p->hProcess, INFINITE);
-		GetExitCodeProcess(p->hProcess, &exitcode);
+		if (WAIT_FAILED == WaitForSingleObject(p->hProcess, INFINITE)
+		    || !GetExitCodeProcess(p->hProcess, &exitcode))
+			return push_error(L);
 		p->status = exitcode;
 	}
 	lua_pushnumber(L, p->status);