diff --git a/src/external/quartic_solver.cpp b/src/external/quartic_solver.cpp
index 0b280e83c29..915020ffaa3 100644
--- a/src/external/quartic_solver.cpp
+++ b/src/external/quartic_solver.cpp
@@ -1,4 +1,5 @@
 #include <algorithm>
+#define _USE_MATH_DEFINES // to make M_PI declared in Intel and MSVC compilers
 #include <cmath>
 #include <complex>
 #include <cstdlib>
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 2ee616f28dc..4b1878c5a2c 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -1,7 +1,8 @@
 #include "openmc/mesh.h"
-#include <algorithm> // for copy, equal, min, min_element
-#include <cmath>     // for ceil
-#include <cstddef>   // for size_t
+#include <algorithm>      // for copy, equal, min, min_element
+#define _USE_MATH_DEFINES // to make M_PI declared in Intel and MSVC compilers
+#include <cmath>          // for ceil
+#include <cstddef>        // for size_t
 #include <gsl/gsl-lite.hpp>
 #include <string>
 
diff --git a/src/plot.cpp b/src/plot.cpp
index 348138570c1..de7d475e1c5 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -1,6 +1,8 @@
 #include "openmc/plot.h"
 
 #include <algorithm>
+#define _USE_MATH_DEFINES // to make M_PI declared in Intel and MSVC compilers
+#include <cmath>
 #include <cstdio>
 #include <fstream>
 #include <sstream>