diff --git a/src/xspice/tlines/tline_common.h b/src/xspice/tlines/tline_common.h
index 2d51dcc61..a9da27ac6 100644
--- a/src/xspice/tlines/tline_common.h
+++ b/src/xspice/tlines/tline_common.h
@@ -23,24 +23,29 @@
 #define TLINE_COMMON_H
 
 // Constants
-#define Z0 (120*M_PI)
-#define z0 50.0
-#define MU0 (4*M_PI*1e-7)
-
-#define C0 299792458.0
-
-#define GMIN 1e-12
 
 #ifdef _MSC_VER
-#define M_E        2.7182818284590452354    // e
+#ifndef M_E
+  #define M_E        2.7182818284590452354    // e
+#endif
+#ifndef M_PI
+  #define M_PI       3.14159265358979323846   // pi
+#endif
 #define M_LN2      0.69314718055994530942   // log_e 2
-#define M_PI       3.14159265358979323846   // pi
 #define M_PI_2     1.57079632679489661923   // pi/2
 #define M_PI_4     0.785398163397448309616  // pi/4
 #define M_1_PI     0.318309886183790671538  // 1/pi
 #define M_2_PI     0.636619772367581343076  // 2/pi
 #endif
 
+#define Z0 (120*M_PI)
+#define z0 50.0
+#define MU0 (4*M_PI*1e-7)
+
+#define C0 299792458.0
+
+#define GMIN 1e-12
+
 // Functions
 #define sqr(x) (x*x)
 #define cubic(x) (x*x*x)