diff --git a/lua/git/object.lua b/lua/git/object.lua
index eaa502c..22e8876 100644
--- a/lua/git/object.lua
+++ b/lua/git/object.lua
@@ -337,10 +337,45 @@ local function side_buf(r, blob, path)
 end
 
 ---@param r ow.Git.Repo
+---@param commit string
+---@param parent boolean
+---@param path string
+---@return integer?
+local function commit_side_buf(r, commit, parent, path)
+    local rev = parent and (commit .. "^") or commit
+    local sha = r:rev_parse(rev, false)
+    if not sha then
+        return nil
+    end
+    if not r:rev_parse(sha .. ":" .. path, false) then
+        return nil
+    end
+    return M.buf_for(r, Revision.new({ base = sha, path = path }))
+end
+
+---@param r ow.Git.Repo
+---@param commit string?
+---@param parent boolean
 ---@param blob string?
 ---@param path string
-local function load_side(r, blob, path)
-    local buf = side_buf(r, blob, path)
+---@return integer?
+local function side(r, commit, parent, blob, path)
+    if commit then
+        local buf = commit_side_buf(r, commit, parent, path)
+        if buf then
+            return buf
+        end
+    end
+    return side_buf(r, blob, path)
+end
+
+---@param r ow.Git.Repo
+---@param commit string?
+---@param parent boolean
+---@param blob string?
+---@param path string
+local function load_side(r, commit, parent, blob, path)
+    local buf = side(r, commit, parent, blob, path)
     if not buf then
         util.error("no content for %s", path)
         return
@@ -350,14 +385,15 @@ local function load_side(r, blob, path)
 end
 
 ---@param r ow.Git.Repo
+---@param commit string?
 ---@param section ow.Git.DiffSection
-local function open_section(r, section)
+local function open_section(r, commit, section)
     if not section.blob_a or not section.blob_b then
         util.error("no index line, cannot determine blob SHAs")
         return
     end
-    local left = side_buf(r, section.blob_a, section.path_a)
-    local right = side_buf(r, section.blob_b, section.path_b)
+    local left = side(r, commit, true, section.blob_a, section.path_a)
+    local right = side(r, commit, false, section.blob_b, section.path_b)
     if left and right then
         vim.cmd.normal({ "m'", bang = true })
         vim.api.nvim_set_current_buf(right)
@@ -377,6 +413,21 @@ local function open_section(r, section)
     vim.api.nvim_set_current_buf(buf)
 end
 
+---@param r ow.Git.Repo
+---@param buf integer
+---@return string?
+local function commit_in_buf(r, buf)
+    local name = vim.api.nvim_buf_get_name(buf)
+    if not vim.startswith(name, M.URI_PREFIX) then
+        return nil
+    end
+    local rev = M.parse_uri(name)
+    if not rev or not rev.base or rev.path then
+        return nil
+    end
+    return r:rev_parse(rev.base .. "^{commit}", false)
+end
+
 ---@class ow.Git.Object.OpenOpts
 ---@field split (false|"above"|"below"|"left"|"right")?
 
@@ -423,7 +474,7 @@ function M.open_under_cursor()
         line:match("^%d+ (%w+) (%x+)\t(.+)$")
     if entry_sha then
         if entry_type == "blob" then
-            load_side(r, entry_sha, entry_name --[[@as string]])
+            load_side(r, nil, false, entry_sha, entry_name --[[@as string]])
         else
             M.open(r, entry_sha, { split = false })
         end
@@ -435,24 +486,26 @@ function M.open_under_cursor()
         return false
     end
 
+    local commit = commit_in_buf(r, vim.api.nvim_get_current_buf())
+
     if line:match("^diff %-%-git ") then
-        open_section(r, section)
+        open_section(r, commit, section)
         return true
     end
     if line:match("^%-%-%- ") then
-        load_side(r, section.blob_a, section.path_a)
+        load_side(r, commit, true, section.blob_a, section.path_a)
         return true
     end
     if line:match("^%+%+%+ ") then
-        load_side(r, section.blob_b, section.path_b)
+        load_side(r, commit, false, section.blob_b, section.path_b)
         return true
     end
     local prefix = line:sub(1, 1)
     if prefix == "+" then
-        load_side(r, section.blob_b, section.path_b)
+        load_side(r, commit, false, section.blob_b, section.path_b)
         return true
     elseif prefix == "-" then
-        load_side(r, section.blob_a, section.path_a)
+        load_side(r, commit, true, section.blob_a, section.path_a)
         return true
     end
     return false
diff --git a/test/git/blame_test.lua b/test/git/blame_test.lua
index 28a4510..b75fd79 100644
--- a/test/git/blame_test.lua
+++ b/test/git/blame_test.lua
@@ -473,19 +473,20 @@ t.test(
         local object = require("git.object")
         local dir = h.make_repo({ ["a.txt"] = "alpha\nbeta\ngamma\n" })
         local sha = h.git(dir, "rev-parse", "HEAD").stdout
+        local tree = h.git(dir, "rev-parse", "HEAD^{tree}").stdout
         local blob = h.git(dir, "rev-parse", "HEAD:a.txt").stdout
         local r = assert(require("git.core.repo").resolve(dir))
 
-        object.open(r, sha, { split = false })
-        local commit_buf = vim.api.nvim_get_current_buf()
+        object.open(r, tree, { split = false })
+        local tree_buf = vim.api.nvim_get_current_buf()
         local found ---@type integer?
-        for i, l in ipairs(vim.api.nvim_buf_get_lines(commit_buf, 0, -1, false)) do
-            if l == "+++ b/a.txt" then
+        for i, l in ipairs(vim.api.nvim_buf_get_lines(tree_buf, 0, -1, false)) do
+            if l:match("^%d+ blob %x+\ta%.txt$") then
                 found = i
                 break
             end
         end
-        local lnum = assert(found, "expected a +++ b/a.txt line")
+        local lnum = assert(found, "expected an a.txt tree entry")
         vim.api.nvim_win_set_cursor(0, { lnum, 0 })
         t.truthy(object.open_under_cursor())
         local gbuf = vim.api.nvim_get_current_buf()
diff --git a/test/git/object_test.lua b/test/git/object_test.lua
index b90f9ee..bbe9a82 100644
--- a/test/git/object_test.lua
+++ b/test/git/object_test.lua
@@ -202,18 +202,58 @@ t.test("open_under_cursor on a 'parent <sha>' line opens the parent", function()
     t.eq(vim.api.nvim_buf_get_name(0), "git://" .. parent_sha)
 end)
 
-t.test("open_under_cursor on a '+++ b/<path>' line loads the blob", function()
-    local dir = h.make_repo({ ["a.txt"] = "first\n" })
-    local r = assert(require("git.core.repo").resolve(dir))
-    local blob_sha = h.git(dir, "rev-parse", "HEAD:a.txt").stdout
+t.test(
+    "open_under_cursor on a '+++ b/<path>' line opens the file at the commit",
+    function()
+        local dir = h.make_repo({ ["a.txt"] = "first\n" })
+        local r = assert(require("git.core.repo").resolve(dir))
+        local commit_sha = h.git(dir, "rev-parse", "HEAD").stdout
 
-    object.open(r, "HEAD", { split = false })
-    local lnum = assert(find_line(0, "+++ b/a.txt"), "expected a +++ line")
-    vim.api.nvim_win_set_cursor(0, { lnum, 0 })
+        object.open(r, "HEAD", { split = false })
+        local lnum = assert(find_line(0, "+++ b/a.txt"), "expected a +++ line")
+        vim.api.nvim_win_set_cursor(0, { lnum, 0 })
 
-    t.truthy(object.open_under_cursor())
-    t.eq(vim.api.nvim_buf_get_name(0), "git://" .. blob_sha)
-end)
+        t.truthy(object.open_under_cursor())
+        t.eq(vim.api.nvim_buf_get_name(0), "git://" .. commit_sha .. ":a.txt")
+    end
+)
+
+t.test(
+    "open_under_cursor on a '--- a/<path>' line opens the parent at that path",
+    function()
+        local dir = h.make_repo({ ["a.txt"] = "first\n" })
+        t.write(dir, "a.txt", "second\n")
+        h.git(dir, "add", "a.txt")
+        h.git(dir, "commit", "-q", "-m", "second")
+        local r = assert(require("git.core.repo").resolve(dir))
+        local parent_sha = h.git(dir, "rev-parse", "HEAD~").stdout
+
+        object.open(r, "HEAD", { split = false })
+        local lnum = assert(find_line(0, "--- a/a.txt"), "expected a --- line")
+        vim.api.nvim_win_set_cursor(0, { lnum, 0 })
+
+        t.truthy(object.open_under_cursor())
+        t.eq(vim.api.nvim_buf_get_name(0), "git://" .. parent_sha .. ":a.txt")
+    end
+)
+
+t.test(
+    "open_under_cursor on a tree-entry blob still uses the bare blob URI",
+    function()
+        local dir = h.make_repo({ ["a.txt"] = "first\n" })
+        local r = assert(require("git.core.repo").resolve(dir))
+        local tree_sha = h.git(dir, "rev-parse", "HEAD^{tree}").stdout
+        local blob_sha = h.git(dir, "rev-parse", "HEAD:a.txt").stdout
+
+        object.open(r, tree_sha, { split = false })
+        local lnum =
+            assert(find_line(0, "100644 blob "), "expected a tree entry line")
+        vim.api.nvim_win_set_cursor(0, { lnum, 0 })
+
+        t.truthy(object.open_under_cursor())
+        t.eq(vim.api.nvim_buf_get_name(0), "git://" .. blob_sha)
+    end
+)
 
 t.test("open_under_cursor returns false on a non-dispatchable line", function()
     local dir = h.make_repo({ a = "first\n" })