diff --git a/src/libgcrypt.h b/src/libgcrypt.h
index 1f773225..e302bf63 100644
--- a/src/libgcrypt.h
+++ b/src/libgcrypt.h
@@ -116,7 +116,7 @@
 
 #define ssh2_bn                        struct gcry_mpi
 #define ssh2_bn_init()                 gcry_mpi_new(0)
-#define ssh2_bn_set_word(bn, word)     gcry_mpi_set_ui(bn, word)
+#define ssh2_bn_set_word(bn, word)     (gcry_mpi_set_ui(bn, word) ? 0 : 1)
 #define ssh2_bn_from_bin(bn, bin, len) \
     gcry_mpi_scan(bn, GCRYMPI_FMT_USG, bin, len, NULL)
 #define ssh2_bn_to_bin(bn, bin) \