diff --git a/Cantera/src/converters/ck2ct.cpp b/Cantera/src/converters/ck2ct.cpp
index ce1d81b35..464ab8283 100644
--- a/Cantera/src/converters/ck2ct.cpp
+++ b/Cantera/src/converters/ck2ct.cpp
@@ -27,6 +27,7 @@ using namespace std;
 #include "writelog.h"
 
 #include "ck2ct.h"
+#include "stringUtils.h"
 #include <time.h>
 #include "ct_defs.h"
 #include "ctml.h"
diff --git a/Cantera/src/numerics/DenseMatrix.cpp b/Cantera/src/numerics/DenseMatrix.cpp
index 2e83a27c8..762e4e393 100755
--- a/Cantera/src/numerics/DenseMatrix.cpp
+++ b/Cantera/src/numerics/DenseMatrix.cpp
@@ -13,6 +13,7 @@
 #include "ctlapack.h"
 #include "utilities.h"
 #include "DenseMatrix.h"
+#include "stringUtils.h"
 
 namespace Cantera {
 
diff --git a/Cantera/src/thermo/Elements.cpp b/Cantera/src/thermo/Elements.cpp
index 0022241ef..945654dfd 100644
--- a/Cantera/src/thermo/Elements.cpp
+++ b/Cantera/src/thermo/Elements.cpp
@@ -26,6 +26,7 @@
 #include "xml.h"
 #include "ctml.h"
 #include "ctexceptions.h"
+#include "stringUtils.h"
 
 using namespace ctml;
 using namespace std;