diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5fe8eb30e..bd149f573 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,7 @@ project(
   LANGUAGES C CXX Fortran)
 
 set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
+set(CMAKE_C_STANDARD 17)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
diff --git a/expui/ParticleIterator.H b/expui/ParticleIterator.H
index 188e9ee1d..0130ec1c2 100644
--- a/expui/ParticleIterator.H
+++ b/expui/ParticleIterator.H
@@ -3,6 +3,7 @@
 
 #include <ParticleReader.H>
 #include <functional>
+#include <cstdint>
 
 namespace Utility
 {
diff --git a/exputil/GaussCore.c b/exputil/GaussCore.c
index 52acb210b..cf809e381 100644
--- a/exputil/GaussCore.c
+++ b/exputil/GaussCore.c
@@ -17,6 +17,7 @@
 
 #include <stdio.h>		/* for error messages */
 #include <stdlib.h>
+#include <stdbool.h>
 #include "GaussCore.h"
 
 #define GaussEPS 1.0e-12
@@ -56,15 +57,13 @@ static int n1;
 void GaussMaster(int n, double alpha, double beta, int conflag,
 		 double abscis[], double weight[])
 {
-#define FALSE 0
-#define  TRUE 1
-    typedef int bool;
     int k, m;
     int below;
     double t, min, max, Glob;
     double delta, Qp;
     double temp;
     bool ok;
+
 #define junk1 &delta
 #define junk2 &Qp
     
@@ -170,7 +169,7 @@ void GaussMaster(int n, double alpha, double beta, int conflag,
 	     -Desirable improvement:
 	      include machine roundoff in equality tests.
 	  */
-	    ok= FALSE;
+	    ok= false;
 	    do {
 		if (Qp==0)  break;
 		delta/= -Qp;
@@ -182,7 +181,7 @@ void GaussMaster(int n, double alpha, double beta, int conflag,
 		    delta*= (1+t);
 		}
 		ok = (min <= temp) && (temp <= max);
-	    } while (FALSE);
+	    } while (false);
 
 	    if (ok) t=temp;		/* use Newton iterate... */
 	    else t= (min + max)/2;	/* ...or bisect to recover */
@@ -197,8 +196,6 @@ void GaussMaster(int n, double alpha, double beta, int conflag,
     }
 #undef junk1
 #undef junk2
-#undef  TRUE
-#undef FALSE
 }
 
 
diff --git a/include/cxxopts.H b/include/cxxopts.H
index 068e7ab6d..f22568196 100644
--- a/include/cxxopts.H
+++ b/include/cxxopts.H
@@ -27,6 +27,7 @@ THE SOFTWARE.
 
 #include <cctype>
 #include <cstring>
+#include <cstdint>
 #include <exception>
 #include <iostream>
 #include <limits>