diff --git a/src/lint/linter/xhpast/rules/ArcanistFormattedStringXHPASTLinterRule.php b/src/lint/linter/xhpast/rules/ArcanistFormattedStringXHPASTLinterRule.php
--- a/src/lint/linter/xhpast/rules/ArcanistFormattedStringXHPASTLinterRule.php
+++ b/src/lint/linter/xhpast/rules/ArcanistFormattedStringXHPASTLinterRule.php
@@ -82,7 +82,12 @@
       }
 
       $format = $parameters->getChildByIndex($start);
-      if ($format->getTypeName() != 'n_STRING_SCALAR') {
+      if (!$format->isConstantString()) {
+
+        // TODO: When this parameter is not a constant string, the call may
+        // be unsafe. We should make some attempt to warn about this for
+        // "qsprintf()" and other security-sensitive functions.
+
         continue;
       }
 
diff --git a/src/lint/linter/xhpast/rules/__tests__/formatted-string/formatted-string.lint-test b/src/lint/linter/xhpast/rules/__tests__/formatted-string/formatted-string.lint-test
--- a/src/lint/linter/xhpast/rules/__tests__/formatted-string/formatted-string.lint-test
+++ b/src/lint/linter/xhpast/rules/__tests__/formatted-string/formatted-string.lint-test
@@ -11,12 +11,17 @@
 queryfx(null, 'x', 'y');
 
 foobar(null, null, '%s');
+
+pht('x %s y');
+pht('x %s y'.'z');
 ~~~~~~~~~~
 error:3:1:XHP54:Formatted String
 error:7:1:XHP54:Formatted String
 error:8:1:XHP54:Formatted String
 error:11:1:XHP54:Formatted String
 error:13:1:XHP54:Formatted String
+error:15:1:XHP54:Formatted String
+error:16:1:XHP54:Formatted String
 ~~~~~~~~~~
 ~~~~~~~~~~
 {