diff --git a/Modules/getbuildinfo.c b/Modules/getbuildinfo.c
index c70126d..ac51881 100644
--- a/Modules/getbuildinfo.c
+++ b/Modules/getbuildinfo.c
@@ -42,7 +42,9 @@
 const char *
 Py_GetBuildInfo(void)
 {
-    static char buildinfo[50];
+    static char buildinfo[50 + sizeof HGVERSION +
+                          ((sizeof HGTAG > sizeof HGBRANCH) ?
+                           sizeof HGTAG : sizeof HGBRANCH)];
     const char *revision = _Py_hgversion();
     const char *sep = *revision ? ":" : "";
     const char *hgid = _Py_hgidentifier();