diff --git a/IBPSA/Resources/C-Sources/fileWriterFree.c b/IBPSA/Resources/C-Sources/fileWriterFree.c
index 4085c48ca1..0c4ac49c91 100644
--- a/IBPSA/Resources/C-Sources/fileWriterFree.c
+++ b/IBPSA/Resources/C-Sources/fileWriterFree.c
@@ -2,6 +2,10 @@
  *
  * Michael Wetter, LBNL                     2018-05-12
  */
+
+#ifndef IBPSA_FILEWRITERFree_c
+#define IBPSA_FILEWRITERFree_c
+
 #include <stdlib.h>
 #include <stdio.h>
 #include "ModelicaUtilities.h"
@@ -62,3 +66,5 @@ void fileWriterFree(void* ptrFileWriter){
 
   return;
 }
+
+#endif
diff --git a/IBPSA/Resources/C-Sources/fileWriterStructure.c b/IBPSA/Resources/C-Sources/fileWriterStructure.c
index 15fa6f8e2a..fafbbc18b8 100644
--- a/IBPSA/Resources/C-Sources/fileWriterStructure.c
+++ b/IBPSA/Resources/C-Sources/fileWriterStructure.c
@@ -1,6 +1,9 @@
 #ifndef IBPSA_FILEWRITERStructure_c
 #define IBPSA_FILEWRITERStructure_c
 
+#include <stdlib.h>
+#include <string.h>
+
 #include "ModelicaUtilities.h"
 
 #include "fileWriterStructure.h"
diff --git a/IBPSA/Resources/C-Sources/jsonWriterInit.c b/IBPSA/Resources/C-Sources/jsonWriterInit.c
index 9d8ffbe88b..5e19354b49 100644
--- a/IBPSA/Resources/C-Sources/jsonWriterInit.c
+++ b/IBPSA/Resources/C-Sources/jsonWriterInit.c
@@ -5,6 +5,12 @@
  * Filip Jorissen, KU Leuven
  */
 
+#ifndef IBPSA_JSONWRITERINIT_c
+#define IBPSA_JSONWRITERINIT_c
+
+#include <stdlib.h>
+#include <string.h>
+
 #include "fileWriterStructure.c"
 #include "ModelicaUtilities.h"
 
@@ -90,3 +96,5 @@ void writeJson(void *ptrFileWriter,  const double* varVals, const int numVals){
   if (fclose(fOut) == EOF)
     ModelicaFormatError("In writeJson.c: Returned an error when closing %s.", ID->fileWriterName);
 }
+
+#endif