diff --git a/xs/Build.PL b/xs/Build.PL
index 23b10273d..3726879bf 100644
--- a/xs/Build.PL
+++ b/xs/Build.PL
@@ -78,9 +78,7 @@ if ($^O eq 'darwin') {
     }
 }
 if ($mswin) {
-    # In case windows.h is included, we don't want the min / max macros to be active.
-    # If <math.h> is included, we want the #defines to be active (M_PI etc.)
-    push @cflags, qw(-DNOMINMAX -D_USE_MATH_DEFINES);
+    push @cflags, qw(-DNOMINMAX);
 }
 
 my @INC  = qw(-Isrc/libslic3r);
diff --git a/xs/src/libslic3r/Fill/FillGyroid.cpp b/xs/src/libslic3r/Fill/FillGyroid.cpp
index eddc00bb5..01c652c5c 100644
--- a/xs/src/libslic3r/Fill/FillGyroid.cpp
+++ b/xs/src/libslic3r/Fill/FillGyroid.cpp
@@ -1,7 +1,6 @@
 #include "../ClipperUtils.hpp"
 #include "../PolylineCollection.hpp"
 #include "../Surface.hpp"
-#define _USE_MATH_DEFINES
 #include <cmath>
 #include <algorithm>
 #include <iostream>
diff --git a/xs/src/libslic3r/libslic3r.h b/xs/src/libslic3r/libslic3r.h
index d178c6c64..7efb563bd 100644
--- a/xs/src/libslic3r/libslic3r.h
+++ b/xs/src/libslic3r/libslic3r.h
@@ -4,7 +4,12 @@
 // this needs to be included early for MSVC (listing it in Build.PL is not enough)
 #include <ostream>
 #include <iostream>
+
+// Otherwise #defines like M_PI are undeclared under Visual Studio
+#ifndef _USE_MATH_DEFINES
 #define _USE_MATH_DEFINES
+#endif
+
 #include <math.h>
 #include <queue>
 #include <sstream>