diff --git a/analyze_structure.lua b/analyze_structure.lua
index 07a7f7f..f215869 100644
--- a/analyze_structure.lua
+++ b/analyze_structure.lua
@@ -211,13 +211,21 @@ end
 
 --------------------------------------------------------------------------------
 
-local function analyze_structure (root, max_depth)
-    if type(root) ~= 'table' then  return {}  end
-    assert(type(root) == 'table')
+local function analyze_structure (root, max_depth, info)
+    -- Argument fixing
+    local info  =  info or {}
     local max_depth = max_depth or math.huge
-    assert(type(max_depth) == 'number')
 
-    local info, visited, next_mark, depth  =  { root = root }, {}, 1, { [root] = 0 }
+    -- Quick return
+    if type(root) ~= 'table' then  return info  end
+
+    -- Error checking
+    assert(type(root) == 'table')
+
+    if type(max_depth) ~= 'number' then  error(('[pretty/internal]: Bad argument #2, expected number, got %s (%s)'):format(max_depth, type(max_depth)), 2)  end
+
+    info.root  =  info.root or root
+    local visited, next_mark, depth  =  {}, 1, { [root] = 0 }
     local queue  =  { root, bottom = 1, top = 2 }
 
     while queue.bottom < queue.top do
diff --git a/test/test_analyze_structure.lua b/test/test_analyze_structure.lua
index 95f2ee8..4ac85ff 100644
--- a/test/test_analyze_structure.lua
+++ b/test/test_analyze_structure.lua
@@ -262,6 +262,21 @@ SUITE:addTest('next_mark does not escape', function ()
     assert(not info.next_mark)
 end)
 
+SUITE:addTest('We can extend an already existing info table', function ()
+    local tab1, tab2  =  {}, {}
+    local info  = analyze_structure( tab1 )
+    analyze_structure( tab2, math.huge, info )
+    assert(info[tab1])
+    assert(info[tab2])
+end)
+
+SUITE:addTest('When we extend an info table, we retain the previous root', function ()
+    local tab1, tab2  =  {}, {}
+    local info  = analyze_structure( tab1 )
+    analyze_structure( tab2, math.huge, info )
+    assert(tab1 == info.root)
+end)
+
 --------------------------------------------------------------------------------
 
 return SUITE