--- x/coreutils/dd.c
+++ y/coreutils/dd.c
@@ -30,6 +30,9 @@
 #include <signal.h>  // For FEATURE_DD_SIGNAL_HANDLING
 #include "busybox.h"
 
+#ifdef __x86_64
+#undef ftruncate
+#endif
 static const struct suffix_mult dd_suffixes[] = {
 	{ "c", 1 },
        { "w", 2 },