diff --git a/src/mac/carbon/dc.cpp b/src/mac/carbon/dc.cpp
index 356e35848c..aaa3df65f4 100644
--- a/src/mac/carbon/dc.cpp
+++ b/src/mac/carbon/dc.cpp
@@ -38,7 +38,9 @@ IMPLEMENT_ABSTRACT_CLASS(wxDC, wxObject)
 #define twips2mm		0.0176388888889
 #define mm2pt			2.83464566929
 #define pt2mm			0.352777777778
+#ifndef __UNIX__
 const double M_PI = 3.14159265358979 ;
+#endif
 const double RAD2DEG  = 180.0 / M_PI;
 
 //-----------------------------------------------------------------------------
diff --git a/src/mac/dc.cpp b/src/mac/dc.cpp
index 356e35848c..aaa3df65f4 100644
--- a/src/mac/dc.cpp
+++ b/src/mac/dc.cpp
@@ -38,7 +38,9 @@ IMPLEMENT_ABSTRACT_CLASS(wxDC, wxObject)
 #define twips2mm		0.0176388888889
 #define mm2pt			2.83464566929
 #define pt2mm			0.352777777778
+#ifndef __UNIX__
 const double M_PI = 3.14159265358979 ;
+#endif
 const double RAD2DEG  = 180.0 / M_PI;
 
 //-----------------------------------------------------------------------------