diff --git a/Misc/NEWS b/Misc/NEWS
index 990f4d6c92f..90e3cc188c5 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.3.1
 Core and Builtins
 -----------------
 
+- Issue #15965: Explicitly cast AT_FDCWD as (int).  Required on Solaris 10
+  (which defines AT_FDCWD as 0xffd19553), harmless on other platforms.
+
 - Issue #15926: Fix crash after multiple reinitializations of the interpreter.
 
 - Issue #15895: Fix FILE pointer leak in one error branch of
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 54f6cd2b22c..e0efebfe1b0 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -414,7 +414,14 @@ win32_warn_bytes_api()
 
 
 #ifdef AT_FDCWD
-#define DEFAULT_DIR_FD AT_FDCWD
+/*
+ * Why the (int) cast?  Solaris 10 defines AT_FDCWD as 0xffd19553 (-3041965);
+ * without the int cast, the value gets interpreted as uint (4291925331),
+ * which doesn't play nicely with all the initializer lines in this file that
+ * look like this:
+ *      int dir_fd = DEFAULT_DIR_FD;
+ */
+#define DEFAULT_DIR_FD (int)AT_FDCWD
 #else
 #define DEFAULT_DIR_FD (-100)
 #endif