diff --git a/g10/export.c b/g10/export.c
index a9eba1544..8a4f6f1f3 100644
--- a/g10/export.c
+++ b/g10/export.c
@@ -985,7 +985,7 @@ transfer_format_to_openpgp (gcry_sexp_t s_pgp, PKT_public_key *pk)
           unsigned int nbits = valuelen*8;
           const unsigned char *p = value;
 
-          if (nbits >= 8 && !(*p & 0x80))
+          if (*p && nbits >= 8 && !(*p & 0x80))
             if (--nbits >= 7 && !(*p & 0x40))
               if (--nbits >= 6 && !(*p & 0x20))
                 if (--nbits >= 5 && !(*p & 0x10))
diff --git a/g10/pkglue.c b/g10/pkglue.c
index cd6e90838..13f8e2f03 100644
--- a/g10/pkglue.c
+++ b/g10/pkglue.c
@@ -71,7 +71,7 @@ sexp_extract_param_sos (gcry_sexp_t sexp, const char *param, gcry_mpi_t *r_sos)
           unsigned int nbits = buflen*8;
           unsigned char *p = p0;
 
-          if (nbits >= 8 && !(*p & 0x80))
+          if (*p && nbits >= 8 && !(*p & 0x80))
             if (--nbits >= 7 && !(*p & 0x40))
               if (--nbits >= 6 && !(*p & 0x20))
                 if (--nbits >= 5 && !(*p & 0x10))