diff --git a/all.h b/all.h
index d8f73b0..7e149f9 100644
--- a/all.h
+++ b/all.h
@@ -527,8 +527,12 @@ global const u64 MAX_u64 = 0xffffffffffffffffull;
 global const u32 MAX_u32 = 0xffffffff;
 global const u16 MAX_u16 = 0xffff;
 global const u8  MAX_u8  = 0xff;
+#ifndef EULERS_E
 #define EULERS_E (2.71828)
+#endif
+#ifndef PI
 #define PI (3.14159265358979323846)
+#endif
 
 ///// CUSTOM ENTRY POINT
 /* TODO?