diff --git a/library/bignum.c b/library/bignum.c
index 0e39e3a..c4eb7b0 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1201,7 +1201,10 @@
         /* If we ran out of space for the carry, it means that the result
          * is negative. */
         if( n == X->n )
-            return( MBEDTLS_ERR_MPI_NEGATIVE_VALUE );
+        {
+            ret = MBEDTLS_ERR_MPI_NEGATIVE_VALUE;
+            goto cleanup;
+        }
         --X->p[n];
     }