diff --git a/crypto/srp/srp_vfy.c b/crypto/srp/srp_vfy.c
index 6889a6bded77ef32f0e42aff59dd479438423a87..179f9a1a2c4b2e2d116eda1ebe37d292b6511557 100644
--- a/crypto/srp/srp_vfy.c
+++ b/crypto/srp/srp_vfy.c
@@ -93,6 +93,9 @@ static int t_fromb64(unsigned char *a, const char *src)
 		else a[i] = loc - b64table;
 		++i;
 		}
+	/* if nothing valid to process we have a zero length response */
+	if (i == 0)
+		return 0;
 	size = i;
 	i = size - 1;
 	j = size;