diff --git a/libr/util/mem.c b/libr/util/mem.c
index d78c3161eb..d7005e1cb0 100644
--- a/libr/util/mem.c
+++ b/libr/util/mem.c
@@ -143,8 +143,8 @@ R_API void r_mem_copybits_delta(ut8 *dst, int doff, const ut8 *src, int soff, in
 		eprintf ("SHIT SHIT SHIT!\n");
 	}
 	for (int i = 0; i < bits; ++i) {
-		ut8 c = readbit (src, bits + soff);
-		writebit (dst, bits + soff, c);
+		ut8 c = readbit (src, i + soff);
+		writebit (dst, i + soff, c);
 	}
 }