diff --git a/Crystal.tmLanguage b/Crystal.tmLanguage
index a938faf..3fd83de 100644
--- a/Crystal.tmLanguage
+++ b/Crystal.tmLanguage
@@ -716,6 +716,12 @@
 			<string>string.quoted.double.crystal</string>
 			<key>patterns</key>
 			<array>
+				<dict>
+					<key>match</key>
+					<string>%([ +-0#]+)?([0-9]+)?(\.[0-9]+)?[bdioxXeEfgGaAcs%]</string>
+					<key>name</key>
+					<string>constant.other.placeholder.crystal</string>
+				</dict>
 				<dict>
 					<key>include</key>
 					<string>#interpolated_crystal</string>