diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -26,6 +26,7 @@
 
 # libphutil
 /src/.phutil_module_cache
+/src/.cache
 /support/phutiltestlib/.phutil_module_cache
 
 # This file overrides "default.pem" if present.
diff --git a/src/aphront/writeguard/AphrontWriteGuard.php b/src/aphront/writeguard/AphrontWriteGuard.php
--- a/src/aphront/writeguard/AphrontWriteGuard.php
+++ b/src/aphront/writeguard/AphrontWriteGuard.php
@@ -98,7 +98,7 @@
     if ($this->allowDepth > 0) {
       throw new Exception(
         pht(
-          'Imbalanced %s: more % calls than %s calls.',
+          'Imbalanced %s: more %s calls than %s calls.',
           __CLASS__,
           'beginUnguardedWrites()',
           'endUnguardedWrites()'));