diff --git a/progs/glsl/skinning.c b/progs/glsl/skinning.c
index 65ba98348b6..2b96f31d060 100644
--- a/progs/glsl/skinning.c
+++ b/progs/glsl/skinning.c
@@ -16,6 +16,9 @@
 #include <GL/glut.h>
 #include "shaderutil.h"
 
+#ifndef M_PI
+#define M_PI 3.1415926535
+#endif
 
 static char *FragProgFile = "skinning.frag";
 static char *VertProgFile = "skinning.vert";
diff --git a/progs/glsl/texaaline.c b/progs/glsl/texaaline.c
index 7a5ac405bba..2e4f932ad60 100644
--- a/progs/glsl/texaaline.c
+++ b/progs/glsl/texaaline.c
@@ -14,6 +14,9 @@
 #include <GL/glew.h>
 #include <GL/glut.h>
 
+#ifndef M_PI
+#define M_PI 3.1415926535
+#endif
 
 static GLint WinWidth = 300, WinHeight = 300;
 static GLint win = 0;
diff --git a/progs/glsl/twoside.c b/progs/glsl/twoside.c
index a57484f96cc..ce155d64e9e 100644
--- a/progs/glsl/twoside.c
+++ b/progs/glsl/twoside.c
@@ -16,6 +16,9 @@
 #include <GL/glut.h>
 #include "shaderutil.h"
 
+#ifndef M_PI
+#define M_PI 3.1415926535
+#endif
 
 static GLint WinWidth = 300, WinHeight = 300;
 static char *FragProgFile = NULL;