diff --git a/src/mac/carbon/dc.cpp b/src/mac/carbon/dc.cpp
index 7a023ff885..9460b87304 100644
--- a/src/mac/carbon/dc.cpp
+++ b/src/mac/carbon/dc.cpp
@@ -46,8 +46,10 @@ IMPLEMENT_ABSTRACT_CLASS(wxDC, wxObject)
 #define mm2pt            2.83464566929
 #define pt2mm            0.352777777778
 #if !defined( __DARWIN__ ) || defined(__MWERKS__)
+#ifndef M_PI
 const double M_PI = 3.14159265358979 ;
 #endif
+#endif
 const double RAD2DEG  = 180.0 / M_PI;
 const short kEmulatedMode = -1 ;
 const short kUnsupportedMode = -2 ;
diff --git a/src/mac/dc.cpp b/src/mac/dc.cpp
index 7a023ff885..9460b87304 100644
--- a/src/mac/dc.cpp
+++ b/src/mac/dc.cpp
@@ -46,8 +46,10 @@ IMPLEMENT_ABSTRACT_CLASS(wxDC, wxObject)
 #define mm2pt            2.83464566929
 #define pt2mm            0.352777777778
 #if !defined( __DARWIN__ ) || defined(__MWERKS__)
+#ifndef M_PI
 const double M_PI = 3.14159265358979 ;
 #endif
+#endif
 const double RAD2DEG  = 180.0 / M_PI;
 const short kEmulatedMode = -1 ;
 const short kUnsupportedMode = -2 ;