diff --git a/src/libgcrypt.c b/src/libgcrypt.c
index b06be42..819df81 100644
--- a/src/libgcrypt.c
+++ b/src/libgcrypt.c
@@ -401,6 +401,7 @@ _libssh2_dsa_sha1_sign(libssh2_dsa_ctx * dsactx,
     unsigned char zhash[SHA_DIGEST_LENGTH + 1];
     gcry_sexp_t sig_sexp;
     gcry_sexp_t data;
+    gcry_mpi_t tmpi;
     int ret;
     const char *tmp;
     size_t size;
@@ -425,40 +426,45 @@ _libssh2_dsa_sha1_sign(libssh2_dsa_ctx * dsactx,
     }
 
     memset(sig, 0, 40);
+    ret = -1;
 
 /* Extract R. */
 
     data = gcry_sexp_find_token(sig_sexp, "r", 0);
-    if (!data) {
-        ret = -1;
+    if (!data)
         goto out;
-    }
 
-    tmp = gcry_sexp_nth_data(data, 1, &size);
-    if (!tmp || size < 1 || size > 20) {
-        ret = -1;
+    tmpi = gcry_sexp_nth_mpi(data, 1, GCRYMPI_FMT_USG);
+    if (!tmpi)
         goto out;
-    }
 
-    memcpy(sig + (20 - size), tmp, size);
+    gcry_mpi_print(GCRYMPI_FMT_STD, sig, 20, &size, tmpi);
+    if (size < 1)
+        goto out;
+    else if (size < 20) {
+        memmove(sig + (20 - size), sig, size);
+        memset(sig, 0, (20 - size));
+    }
 
     gcry_sexp_release(data);
 
 /* Extract S. */
 
     data = gcry_sexp_find_token(sig_sexp, "s", 0);
-    if (!data) {
-        ret = -1;
+    if (!data)
         goto out;
-    }
 
-    tmp = gcry_sexp_nth_data(data, 1, &size);
-    if (!tmp || size < 1 || size > 20) {
-        ret = -1;
+    tmpi = gcry_sexp_nth_mpi(data, 1, GCRYMPI_FMT_USG);
+    if (!tmpi)
         goto out;
-    }
 
-    memcpy(sig + 20 + (20 - size), tmp, size);
+    gcry_mpi_print(GCRYMPI_FMT_STD, sig + 20, 20, &size, tmpi);
+    if (size < 1)
+        goto out;
+    else if (size < 20) {
+        memmove(sig + 20 + (20 - size), sig + 20, size);
+        memset(sig + 20, 0, (20 - size));
+    }
 
     ret = 0;
   out: