diff --git a/src/land/ArcanistGitLandEngine.php b/src/land/ArcanistGitLandEngine.php
--- a/src/land/ArcanistGitLandEngine.php
+++ b/src/land/ArcanistGitLandEngine.php
@@ -148,8 +148,11 @@
 
     try {
       if ($this->getShouldSquash()) {
+        // NOTE: We're explicitly specifying "--ff" to override the presence
+        // of "merge.ff" options in user configuration.
+
         $api->execxLocal(
-          'merge --no-stat --no-commit --squash -- %s',
+          'merge --no-stat --no-commit --ff --squash -- %s',
           $source);
       } else {
         $api->execxLocal(