diff --git a/README.markdown b/README.markdown
index 9b2ec1f..fe387b8 100644
--- a/README.markdown
+++ b/README.markdown
@@ -173,6 +173,12 @@ buffers in which they appears in the preview window. It does the same thing
 for context except that it gives in the preview the list of projects existing
 in each existing contexts.
 
+If you don't want the preview window to open when performing completion, add the
+following lines to your vimrc:
+
+    au filetype todo setlocal completeopt-=preview
+
+
 ## Hierarchical sort
 
 This fork provides a hierarchical sorting function designed to do by project
diff --git a/autoload/todo.vim b/autoload/todo.vim
index 2842844..e694c17 100644
--- a/autoload/todo.vim
+++ b/autoload/todo.vim
@@ -393,7 +393,11 @@ endfun
 fun! TodoCopyTempItem(item)
     let ret={}
     let ret.word=a:item.word
-    let ret.related=[a:item.related]
+    if has_key(a:item, "related")
+        let ret.related=[a:item.related]
+    else
+        let ret.related=[]
+    endif
     let ret.buffers=[a:item.buffers]
     return ret
 endfun
@@ -423,7 +427,9 @@ fun! todo#Complete(findstart, base)
                     let item={}
                     let item.word=substitute(line,'.*\('.a:base.'\S*\).*','\1',"")
                     let item.buffers=bufname(bufnr)
-                    let item.related=substitute(line,'.*\s\('.opp.'\S\S*\).*','\1',"")
+                    if line =~ '.*\s\('.opp.'\S\S*\).*'
+                        let item.related=substitute(line,'.*\s\('.opp.'\S\S*\).*','\1',"")
+                    endif
                     call add(res,item)
                 endif
             endfor
@@ -436,7 +442,7 @@ fun! todo#Complete(findstart, base)
             for it in res
                 if curitem.word==it.word
                     " Merge results
-                    if index(curitem.related,it.related) <0
+                    if has_key(curitem, "related") && has_key(it, "related") && index(curitem.related,it.related) <0
                         call add(curitem.related,it.related)
                     endif
                     if index(curitem.buffers,it.buffers) <0
diff --git a/doc/todo.txt b/doc/todo.txt
index 087c25f..51851db 100644
--- a/doc/todo.txt
+++ b/doc/todo.txt
@@ -182,6 +182,12 @@ buffers in which they appears in the preview window. It does the same thing
 for context except that it gives in the preview the list of projects existing
 in each existing contexts.
 
+If you don't want the preview window to open when performing completion, add the
+following lines to your vimrc:
+>
+    au filetype todo setlocal completeopt-=preview
+<
+
 ===============================================================================
 5. Hierarchical sort                               *TodoTxt-HierarchicalSort* ~
 
diff --git a/tests/clean-vim.sh b/tests/clean-vim.sh
index 6960d75..8838151 100644
--- a/tests/clean-vim.sh
+++ b/tests/clean-vim.sh
@@ -11,6 +11,7 @@ set rtp+=~/.vim/bundle/vader.vim
 set rtp+=./
 filetype plugin indent on
 syntax enable
+autocmd filetype todo setlocal omnifunc=todo#Complete
 EOF
-) tests/todo.txt
+) $*
 
diff --git a/tests/runtests.sh b/tests/runtests.sh
index d4902b4..5774bfa 100644
--- a/tests/runtests.sh
+++ b/tests/runtests.sh
@@ -11,6 +11,7 @@ set rtp+=~/.vim/bundle/vader.vim
 set rtp+=./
 filetype plugin indent on
 syntax enable
+autocmd filetype todo setlocal omnifunc=todo#Complete
 EOF
 ) +Vader! tests/*.vader && echo Success || exit 1
 
@@ -24,6 +25,7 @@ set rtp+=~/.vim/bundle/vader.vim
 set rtp+=./
 filetype plugin indent on
 syntax enable
+autocmd filetype todo setlocal omnifunc=todo#Complete
 set ignorecase
 EOF
 ) +Vader! tests/*.vader && echo Success || exit 1
@@ -37,6 +39,7 @@ set rtp+=~/.vim/bundle/vader.vim
 set rtp+=./
 filetype plugin indent on
 syntax enable
+autocmd filetype todo setlocal omnifunc=todo#Complete
 set iskeyword+=-
 EOF
 ) +Vader! tests/*.vader && echo Success || exit 1
diff --git a/tests/todo.vader b/tests/todo.vader
index 65f32e9..b70647d 100644
--- a/tests/todo.vader
+++ b/tests/todo.vader
@@ -760,6 +760,33 @@ Then (Is cursor on first non-overdue task?):
 After:
     unlet g:TodoTxtSortDueDateCursorPos
 
+" function todo#Complete(findstart, base) {{{2
+Given todo (Tasks):
+  2017-09-23 Test task +SecretProject @Work due:2017-09-26
+  Tricky lowercase @wrongCaseSelected +selectedWrongCase
+  Project without a context +SecretProject
+Do (Complete context W):
+  Go@W\<C-X>\<C-O>
+Expect todo (Context Work):
+  2017-09-23 Test task +SecretProject @Work due:2017-09-26
+  Tricky lowercase @wrongCaseSelected +selectedWrongCase
+  Project without a context +SecretProject
+  @Work
+Do (Complete project S):
+  Go+S\<C-X>\<C-O>
+Expect todo (Project SecretProject):
+  2017-09-23 Test task +SecretProject @Work due:2017-09-26
+  Tricky lowercase @wrongCaseSelected +selectedWrongCase
+  Project without a context +SecretProject
+  +SecretProject
+Execute (Complete project and switch to preview):
+  :execute "normal Go+\<C-X>\<C-O>\<ESC>"
+  :blast!
+Expect (Project SecretProject):
+  Contexts: @Context
+  Buffers: tests/todo.vader
+  
+
 " file: ftplugin/todo.vim {{{1
 
 " function: TodoFoldLevel(lnum) {{{2