diff --git a/SConstruct b/SConstruct
index 7a177991d..072aefe89 100644
--- a/SConstruct
+++ b/SConstruct
@@ -1100,7 +1100,7 @@ class D1XProgram(DXXProgram):
 'main/bm.c',
 'main/bmread.c',
 'main/collide.c',
-'main/custom.c',
+'main/custom.cpp',
 'main/fireball.c',
 'main/fuelcen.c',
 'main/gamemine.c',
diff --git a/d1x-rebirth/main/custom.c b/d1x-rebirth/main/custom.cpp
similarity index 100%
rename from d1x-rebirth/main/custom.c
rename to d1x-rebirth/main/custom.cpp
diff --git a/d1x-rebirth/main/custom.h b/d1x-rebirth/main/custom.h
index 1fa487bf6..bf15baf7a 100644
--- a/d1x-rebirth/main/custom.h
+++ b/d1x-rebirth/main/custom.h
@@ -4,6 +4,10 @@
 #include "pstypes.h"
 #include "piggy.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* from piggy.c */
 #define DBM_FLAG_LARGE	128		// Flags added onto the flags struct in b
 #define DBM_FLAG_ABM            64
@@ -16,4 +20,8 @@ void load_custom_data(char *level_file);
 
 void custom_close();
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif