diff --git a/library/bignum.c b/library/bignum.c
index 0e587f1..d8b842f 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -887,7 +887,12 @@
 
     if( X == B )
     {
-        const mbedtls_mpi *T = A; A = X; B = T;
+        const mbedtls_mpi *T;
+
+        if( B == A)
+            return mbedtls_mpi_shift_l( X, 1 );
+
+        T = A; A = X; B = T;
     }
 
     if( X != A )