diff --git a/src/misc1.c b/src/misc1.c
index 4f33015..f19c2dc 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -627,6 +627,9 @@
 # ifdef FEAT_CINDENT
 					&& !curbuf->b_p_cin
 # endif
+# ifdef FEAT_EVAL
+					&& *curbuf->b_p_inde == NUL
+# endif
 			);
     int		no_si = FALSE;		/* reset did_si afterwards */
     int		first_char = NUL;	/* init for GCC */
diff --git a/src/testdir/test_smartindent.vim b/src/testdir/test_smartindent.vim
index d00eac9..9e93a55 100644
--- a/src/testdir/test_smartindent.vim
+++ b/src/testdir/test_smartindent.vim
@@ -1,3 +1,4 @@
+" Tests for smartindent
 
 " Tests for not doing smart indenting when it isn't set.
 function! Test_nosmartindent()
@@ -12,3 +13,29 @@
   call assert_equal("		#test", getline(1))
   enew! | close
 endfunction
+
+function MyIndent()
+endfunction
+
+" When 'indentexpr' is set, setting 'si' has no effect.
+function Test_smartindent_has_no_effect()
+  new
+  exe "normal! i\<Tab>one\<Esc>"
+  set noautoindent
+  set smartindent
+  set indentexpr=
+  exe "normal! Gotwo\<Esc>"
+  call assert_equal("\ttwo", getline("$"))
+
+  set indentexpr=MyIndent
+  exe "normal! Gothree\<Esc>"
+  call assert_equal("three", getline("$"))
+
+  delfunction! MyIndent
+  set autoindent&
+  set smartindent&
+  set indentexpr&
+  bwipe!
+endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index c5c39fe..a5a3d68 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    851,
+/**/
     850,
 /**/
     849,