diff --git a/ApplicationLibCode/Application/Tools/RiaStdStringTools.cpp b/ApplicationLibCode/Application/Tools/RiaStdStringTools.cpp
index 786e2c260c..794f1a7b2f 100644
--- a/ApplicationLibCode/Application/Tools/RiaStdStringTools.cpp
+++ b/ApplicationLibCode/Application/Tools/RiaStdStringTools.cpp
@@ -23,6 +23,7 @@
 #include <cctype>
 #include <charconv>
 #include <regex>
+#include <sstream>
 
 const std::string WHITESPACE = " \n\r\t\f\v";