diff --git a/src/list.c b/src/list.c
index 6f475fc..68be034 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1689,6 +1689,7 @@
 	{
 	    int		i;
 	    typval_T	tv;
+	    varnumber_T	val;
 
 	    // set_vim_var_nr() doesn't set the type
 	    set_vim_var_type(VV_KEY, VAR_NUMBER);
@@ -1696,7 +1697,8 @@
 	    for (i = 0; i < b->bv_ga.ga_len; i++)
 	    {
 		tv.v_type = VAR_NUMBER;
-		tv.vval.v_number = blob_get(b, i);
+		val = blob_get(b, i);
+		tv.vval.v_number = val;
 		set_vim_var_nr(VV_KEY, idx);
 		if (filter_map_one(&tv, expr, map, &rem) == FAIL || did_emsg)
 		    break;
@@ -1705,17 +1707,21 @@
 		    emsg(_(e_invalblob));
 		    break;
 		}
-		tv.v_type = VAR_NUMBER;
-		blob_set(b, i, tv.vval.v_number);
-		if (!map && rem)
+		if (map)
+		{
+		    if (tv.vval.v_number != val)
+			blob_set(b, i, tv.vval.v_number);
+		}
+		else if (rem)
 		{
 		    char_u *p = (char_u *)argvars[0].vval.v_blob->bv_ga.ga_data;
 
-		    mch_memmove(p + idx, p + i + 1,
+		    mch_memmove(p + i, p + i + 1,
 					      (size_t)b->bv_ga.ga_len - i - 1);
 		    --b->bv_ga.ga_len;
 		    --i;
 		}
+		++idx;
 	    }
 	}
 	else // argvars[0].v_type == VAR_LIST
diff --git a/src/testdir/test_blob.vim b/src/testdir/test_blob.vim
index a4e9bea..18d9c8a 100644
--- a/src/testdir/test_blob.vim
+++ b/src/testdir/test_blob.vim
@@ -260,18 +260,22 @@
 
 " filter() item in blob
 func Test_blob_filter()
-  let b = 0zDEADBEEF
-  call filter(b, 'v:val != 0xEF')
-  call assert_equal(0zDEADBE, b)
+  call assert_equal(0z, filter(0zDEADBEEF, '0'))
+  call assert_equal(0zADBEEF, filter(0zDEADBEEF, 'v:val != 0xDE'))
+  call assert_equal(0zDEADEF, filter(0zDEADBEEF, 'v:val != 0xBE'))
+  call assert_equal(0zDEADBE, filter(0zDEADBEEF, 'v:val != 0xEF'))
+  call assert_equal(0zDEADBEEF, filter(0zDEADBEEF, '1'))
+  call assert_equal(0z01030103, filter(0z010203010203, 'v:val != 0x02'))
+  call assert_equal(0zADEF, filter(0zDEADBEEF, 'v:key % 2'))
 endfunc
 
 " map() item in blob
 func Test_blob_map()
-  let b = 0zDEADBEEF
-  call map(b, 'v:val + 1')
-  call assert_equal(0zDFAEBFF0, b)
+  call assert_equal(0zDFAEBFF0, map(0zDEADBEEF, 'v:val + 1'))
+  call assert_equal(0z00010203, map(0zDEADBEEF, 'v:key'))
+  call assert_equal(0zDEAEC0F2, map(0zDEADBEEF, 'v:key + v:val'))
 
-  call assert_fails("call map(b, '[9]')", 'E978:')
+  call assert_fails("call map(0z00, '[9]')", 'E978:')
 endfunc
 
 func Test_blob_index()
diff --git a/src/version.c b/src/version.c
index e20bf5d..e26d15e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    121,
+/**/
     120,
 /**/
     119,