diff --git a/Date-Pcalc/src/C_XS/ToolBox.h b/Date-Pcalc/src/C_XS/ToolBox.h

index df6fc1c..8687e47 100644

--- a/Date-Pcalc/src/C_XS/ToolBox.h

+++ b/Date-Pcalc/src/C_XS/ToolBox.h

@@ -93,7 +93,10 @@ typedef  Z_longword         *Z_longwordptr;

     #elif PERL_DARWIN

         #define boolean bool

     #else

-        typedef enum { false = FALSE, true = TRUE } boolean;

+        typedef int boolean;

+        #ifndef I_STDBOOL

+            enum { false, true };

+        #endif 

     #endif

 #endif