diff --git a/tests/sampler/test_parscan.cpp b/tests/sampler/test_parscan.cpp
index 5e7097be0..8dffe97cb 100644
--- a/tests/sampler/test_parscan.cpp
+++ b/tests/sampler/test_parscan.cpp
@@ -1,3 +1,4 @@
+#include <string>
 #include <iostream>
 #include <sstream>
 #include <vector>