diff --git a/syntaxes/chapel.tmLanguage.json b/syntaxes/chapel.tmLanguage.json
index ffd921b..8076cb8 100644
--- a/syntaxes/chapel.tmLanguage.json
+++ b/syntaxes/chapel.tmLanguage.json
@@ -166,6 +166,10 @@
     },
     "string_format": {
       "patterns": [
+        {
+          "match": "(%\\?)",
+          "name": "constant.other.placeholder.chapel"
+        },
         {
           "match": "(%[{]([#]+|[#]*[.][#]+)[}])",
           "name": "constant.other.placeholder.chapel"