diff --git a/src/conf.h b/src/conf.h
index ae6991a9..626566d4 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -292,6 +292,9 @@
 #define index               upx_index
 #define outp                upx_outp
 
+#undef PAGE_MASK
+#undef PAGE_SIZE
+
 
 #undef __attribute_packed
 #if (ACC_CC_GNUC || ACC_CC_INTELC || ACC_CC_PATHSCALE)
diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index 8b09929f..3fdc41cf 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -949,8 +949,6 @@ void PackLinuxElf64amd::pack3(OutputFile *fo, Filter &ft)
     fo->write(&zero, frag);
     len += frag;
 
-#undef PAGE_MASK
-#undef PAGE_SIZE
 #define PAGE_MASK (~0u<<12)
 #define PAGE_SIZE (-PAGE_MASK)
     upx_byte *const p = const_cast<upx_byte *>(getLoader());