diff --git a/CMakeLists.txt b/CMakeLists.txt
index 01f49968..bf39ebfd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.8)
 project(ccls LANGUAGES CXX)
 
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/)
diff --git a/src/messages/textDocument_completion.cc b/src/messages/textDocument_completion.cc
index 13621d00..3f6fa3fb 100644
--- a/src/messages/textDocument_completion.cc
+++ b/src/messages/textDocument_completion.cc
@@ -438,8 +438,8 @@ void MessageHandler::textDocument_completion(CompletionParam &param,
                                              ReplyOnce &reply) {
   static CompleteConsumerCache<std::vector<CompletionItem>> cache;
   std::string path = param.textDocument.uri.GetPath();
-  WorkingFile *file = wfiles->GetFile(path);
-  if (!file) {
+  WorkingFile *wf = wfiles->GetFile(path);
+  if (!wf) {
     reply.NotReady(true);
     return;
   }
@@ -449,9 +449,8 @@ void MessageHandler::textDocument_completion(CompletionParam &param,
   // It shouldn't be possible, but sometimes vscode will send queries out
   // of order, ie, we get completion request before buffer content update.
   std::string buffer_line;
-  if (param.position.line >= 0 &&
-      param.position.line < file->buffer_lines.size())
-    buffer_line = file->buffer_lines[param.position.line];
+  if (param.position.line >= 0 && param.position.line < wf->buffer_lines.size())
+    buffer_line = wf->buffer_lines[param.position.line];
 
   clang::CodeCompleteOptions CCOpts;
   CCOpts.IncludeBriefComments = true;
@@ -487,7 +486,7 @@ void MessageHandler::textDocument_completion(CompletionParam &param,
   std::string filter;
   Position end_pos = param.position;
   Position begin_pos =
-      file->FindStableCompletionSource(param.position, &filter, &end_pos);
+      wf->GetCompletionPosition(param.position, &filter, &end_pos);
 
 #if LLVM_VERSION_MAJOR < 8
   ParseIncludeLineResult preprocess = ParseIncludeLine(buffer_line);
diff --git a/src/messages/textDocument_signatureHelp.cc b/src/messages/textDocument_signatureHelp.cc
index 240aada3..dcb11427 100644
--- a/src/messages/textDocument_signatureHelp.cc
+++ b/src/messages/textDocument_signatureHelp.cc
@@ -143,11 +143,15 @@ void MessageHandler::textDocument_signatureHelp(
 
   std::string path = param.textDocument.uri.GetPath();
   Position begin_pos = param.position;
-  if (WorkingFile *file = wfiles->GetFile(path)) {
-    std::string completion_text;
+  WorkingFile *wf = wfiles->GetFile(path);
+  if (!wf) {
+    reply.NotReady(true);
+    return;
+  }
+  {
+    std::string filter;
     Position end_pos = param.position;
-    begin_pos = file->FindStableCompletionSource(param.position,
-                                                 &completion_text, &end_pos);
+    begin_pos = wf->GetCompletionPosition(param.position, &filter, &end_pos);
   }
 
   SemaManager::OnComplete callback =
diff --git a/src/working_files.cc b/src/working_files.cc
index 37d76c0c..771a208b 100644
--- a/src/working_files.cc
+++ b/src/working_files.cc
@@ -336,21 +336,19 @@ std::optional<int> WorkingFile::GetIndexPosFromBufferPos(int line, int *column,
                           index_lines, is_end);
 }
 
-Position
-WorkingFile::FindStableCompletionSource(Position position,
-                                        std::string *existing_completion,
-                                        Position *replace_end_pos) const {
-  int start = GetOffsetForPosition(position, buffer_content);
+Position WorkingFile::GetCompletionPosition(Position pos, std::string *filter,
+                                            Position *replace_end_pos) const {
+  int start = GetOffsetForPosition(pos, buffer_content);
   int i = start;
   while (i > 0 && isIdentifierBody(buffer_content[i - 1]))
     --i;
 
-  *replace_end_pos = position;
+  *replace_end_pos = pos;
   for (int i = start;
        i < buffer_content.size() && isIdentifierBody(buffer_content[i]); i++)
     replace_end_pos->character++;
 
-  *existing_completion = buffer_content.substr(i, start - i);
+  *filter = buffer_content.substr(i, start - i);
   return GetPositionForOffset(buffer_content, i);
 }
 
diff --git a/src/working_files.hh b/src/working_files.hh
index 00f21371..322c81b9 100644
--- a/src/working_files.hh
+++ b/src/working_files.hh
@@ -50,16 +50,10 @@ struct WorkingFile {
   // Also resolves |column| if not NULL.
   std::optional<int> GetIndexPosFromBufferPos(int line, int *column,
                                               bool is_end);
-  // Returns a relatively stable completion position (it jumps back until there
-  // is a non-alphanumeric character).
-  //
-  // The out param |is_global_completion| is set to true if this looks like a
-  // global completion.
-  // The out param |existing_completion| is set to any existing completion
-  // content the user has entered.
-  Position FindStableCompletionSource(Position position,
-                                        std::string *existing_completion,
-                                        Position *replace_end_pos) const;
+  // Returns the stable completion position (it jumps back until there is a
+  // non-alphanumeric character).
+  Position GetCompletionPosition(Position pos, std::string *filter,
+                                 Position *replace_end_pos) const;
 
 private:
   // Compute index_to_buffer and buffer_to_index.