diff --git a/src/parser/xhpast/bin/PhutilXHPASTBinary.php b/src/parser/xhpast/bin/PhutilXHPASTBinary.php
--- a/src/parser/xhpast/bin/PhutilXHPASTBinary.php
+++ b/src/parser/xhpast/bin/PhutilXHPASTBinary.php
@@ -8,7 +8,7 @@
    * This is the version that would be obtained with an up-to-date XHPAST
    * build. The //actual// XHPAST build version may vary.
    */
-  const EXPECTED_VERSION = '5.5.8/1i';
+  const EXPECTED_VERSION = '5.5.9';
 
   /**
    * The XHPAST build version.
diff --git a/support/xhpast/xhpast.cpp b/support/xhpast/xhpast.cpp
--- a/support/xhpast/xhpast.cpp
+++ b/support/xhpast/xhpast.cpp
@@ -14,7 +14,7 @@
 int main(int argc, char* argv[]) {
   if (argc != 1) {
     // Coupling: modify also src/parser/xhpast/bin/PhutilXHPASTBinary.php
-    cout << "5.5.8/1i\n";
+    cout << "5.5.9\n";
     return 0;
   }