diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 768a4643..965f3451 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -68,9 +68,10 @@ end
 
 
 local function save(filename)
-  doc():save(filename)
-  core.on_doc_save(filename)
-  core.log("Saved \"%s\"", doc().filename)
+  doc():save(filename and core.normalize_to_project_dir(filename))
+  local saved_filename = doc().filename
+  core.on_doc_save(saved_filename)
+  core.log("Saved \"%s\"", saved_filename)
 end
 
 
diff --git a/data/core/common.lua b/data/core/common.lua
index e459476a..379ca795 100644
--- a/data/core/common.lua
+++ b/data/core/common.lua
@@ -247,6 +247,11 @@ local function split_on_slash(s, sep_pattern)
 end
 
 
+function common.path_belongs_to(filename, path)
+  return string.find(filename, path .. PATHSEP, 1, true) == 1
+end
+
+
 function common.relative_path(ref_dir, dir)
   local ref_ls = split_on_slash(ref_dir)
   local dir_ls = split_on_slash(dir)
@@ -259,9 +264,9 @@ function common.relative_path(ref_dir, dir)
   end
   local ups = ""
   for k = i, #ref_ls do
-    ups = ups .. "../"
+    ups = ups .. ".." .. PATHSEP
   end
-  local rel_path = ups .. table.concat(dir_ls, "/", i)
+  local rel_path = ups .. table.concat(dir_ls, PATHSEP, i)
   return rel_path ~= "" and rel_path or "."
 end
 
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 3f1c39cd..b2416d3a 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -66,7 +66,6 @@ end
 
 
 function Doc:set_filename(filename)
-  filename = common.normalize_path(filename)
   self.filename = filename
   self.abs_filename = common.home_encode(system.absolute_path(filename))
 end
diff --git a/data/core/init.lua b/data/core/init.lua
index 45490148..7f904fb7 100644
--- a/data/core/init.lua
+++ b/data/core/init.lua
@@ -732,18 +732,27 @@ function core.pop_clip_rect()
 end
 
 
+function core.normalize_to_project_dir(filename)
+  filename = common.normalize_path(filename)
+  if common.path_belongs_to(filename, core.project_dir) then
+    filename = common.relative_path(core.project_dir, filename)
+  end
+  return filename
+end
+
+
 function core.open_doc(filename)
   if filename then
     -- try to find existing doc for filename
     local abs_filename = system.absolute_path(filename)
     for _, doc in ipairs(core.docs) do
-      if doc.filename
-      and abs_filename == system.absolute_path(doc.filename) then
+      if doc.abs_filename and abs_filename == doc.abs_filename then
         return doc
       end
     end
   end
   -- no existing doc for filename; create new
+  filename = core.normalize_to_project_dir(filename)
   local doc = Doc(filename)
   table.insert(core.docs, doc)
   core.log_quiet(filename and "Opened doc \"%s\"" or "Opened new doc", filename)