diff --git a/src/fileio.c b/src/fileio.c
index a028b22..17490ac 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2944,6 +2944,7 @@
 	 * Avoids accidentally overwriting the file with garbage. */
 	curbuf->b_p_ro = TRUE;
 
+	/* Set the cryptmethod local to the buffer. */
 	crypt_set_cm_option(curbuf, method);
 	if (cryptkey == NULL && !*did_ask)
 	{
diff --git a/src/memline.c b/src/memline.c
index a5053f0..7adb2dc 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -235,6 +235,7 @@
 } upd_block0_T;
 
 #ifdef FEAT_CRYPT
+static void ml_set_mfp_crypt __ARGS((buf_T *buf));
 static void ml_set_b0_crypt __ARGS((buf_T *buf, ZERO_BL *b0p));
 #endif
 static int ml_check_b0_id __ARGS((ZERO_BL *b0p));
@@ -433,6 +434,25 @@
 
 #if defined(FEAT_CRYPT) || defined(PROTO)
 /*
+ * Prepare encryption for "buf" for the current key and method.
+ */
+    static void
+ml_set_mfp_crypt(buf)
+    buf_T	*buf;
+{
+    if (*buf->b_p_key != NUL)
+    {
+	int method_nr = crypt_get_method_nr(buf);
+
+	if (method_nr > CRYPT_M_ZIP)
+	{
+	    /* Generate a seed and store it in the memfile. */
+	    sha2_seed(buf->b_ml.ml_mfp->mf_seed, MF_SEED_LEN, NULL, 0);
+	}
+    }
+}
+
+/*
  * Prepare encryption for "buf" with block 0 "b0p".
  */
     static void
@@ -915,8 +935,19 @@
     ZERO_BL	*b0p;
 
     mfp = buf->b_ml.ml_mfp;
-    if (mfp == NULL || (hp = mf_get(mfp, (blocknr_T)0, 1)) == NULL)
+    if (mfp == NULL)
 	return;
+    hp = mf_get(mfp, (blocknr_T)0, 1);
+    if (hp == NULL)
+    {
+#ifdef FEAT_CRYPT
+	/* Possibly update the seed in the memfile before there is a block0. */
+	if (what == UB_CRYPT)
+	    ml_set_mfp_crypt(buf);
+#endif
+	return;
+    }
+
     b0p = (ZERO_BL *)(hp->bh_data);
     if (ml_check_b0_id(b0p) == FAIL)
 	EMSG(_("E304: ml_upd_block0(): Didn't get block 0??"));
diff --git a/src/option.c b/src/option.c
index 62556b6..f928b3b 100644
--- a/src/option.c
+++ b/src/option.c
@@ -6163,6 +6163,14 @@
 		p_cm = vim_strsave((char_u *)"zip");
 		new_value_alloced = TRUE;
 	    }
+	    /* When using ":set cm=name" the local value is going to be empty.
+	     * Do that here, otherwise the crypt functions will still use the
+	     * local value. */
+	    if ((opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0)
+	    {
+		free_string_option(curbuf->b_p_cm);
+		curbuf->b_p_cm = empty_option;
+	    }
 
 	    /* Need to update the swapfile when the effective method changed.
 	     * Set "s" to the effective old value, "p" to the effective new
diff --git a/src/version.c b/src/version.c
index e980361..b832539 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    403,
+/**/
     402,
 /**/
     401,