diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
index 1871e7b61ca0..d25e9e96c310 100644
--- a/lib/mpi/mpi-cmp.c
+++ b/lib/mpi/mpi-cmp.c
@@ -57,14 +57,12 @@ int mpi_cmp(MPI u, MPI v)
 	if (usize != vsize && !u->sign && !v->sign)
 		return usize - vsize;
 	if (usize != vsize && u->sign && v->sign)
-		return vsize + usize;
+		return vsize - usize;
 	if (!usize)
 		return 0;
 	cmp = mpihelp_cmp(u->d, v->d, usize);
-	if (!cmp)
-		return 0;
-	if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
-		return 1;
-	return -1;
+	if (u->sign)
+		return -cmp;
+	return cmp;
 }
 EXPORT_SYMBOL_GPL(mpi_cmp);
diff --git a/lib/mpi/mpi-internal.h b/lib/mpi/mpi-internal.h
index 60cf765628e9..c65dd1bff45a 100644
--- a/lib/mpi/mpi-internal.h
+++ b/lib/mpi/mpi-internal.h
@@ -84,7 +84,7 @@ static inline int RESIZE_IF_NEEDED(MPI a, unsigned b)
 	do {					\
 		mpi_size_t _i;			\
 		for (_i = 0; _i < (n); _i++)	\
-			(d)[_i] = (d)[_i];	\
+			(d)[_i] = (s)[_i];	\
 	} while (0)
 
 #define MPN_COPY_DECR(d, s, n) \