diff --git a/src/machi_csum_table.erl b/src/machi_csum_table.erl
index 88cc906..b804992 100644
--- a/src/machi_csum_table.erl
+++ b/src/machi_csum_table.erl
@@ -154,32 +154,33 @@ trim(CsumT, Offset, Size, LeftUpdate, RightUpdate) ->
 %% @doc returns whether all bytes in a specific window is continously
 %% trimmed or not
 -spec all_trimmed(table(), non_neg_integer(), non_neg_integer()) -> boolean().
-all_trimmed(CsumT, Left, Right) ->
-    Chunks = find(CsumT, Left, Right),
-    runthru(Chunks, Left, Right).
+all_trimmed(#machi_csum_table{table=T}, Left, Right) ->
+    FoldFun = fun({_, _}, false) ->
+                      false;
+                 ({K, V}, Pos) when is_integer(Pos) andalso Pos =< Right ->
+                      case {sext:decode(K), sext:decode(V)} of
+                          {{Pos, Size}, trimmed} ->
+                              Pos + Size;
+                          {{Offset, Size}, _}
+                            when Offset + Size =< Left ->
+                              Left;
+                          _Eh ->
+                              false
+                      end
+              end,
+    case eleveldb:fold(T, FoldFun, Left, [{verify_checksums, true}]) of
+        false -> false;
+        Right -> true;
+        LastTrimmed when LastTrimmed < Right -> false;
+        _ -> %% LastTrimmed > Pos0, which is a irregular case but ok
+            true
+    end.
 
 %% @doc returns whether all bytes 0-Pos0 is continously trimmed or
 %% not, including header.
 -spec all_trimmed(table(), non_neg_integer()) -> boolean().
-all_trimmed(#machi_csum_table{table=T}, Pos0) ->
-    FoldFun = fun({_, _}, false) ->
-                      false;
-                 ({K, V}, Pos) when is_integer(Pos) andalso Pos =< Pos0 ->
-                      case {sext:decode(K), sext:decode(V)} of
-                          {{Pos, Size}, trimmed} ->
-                              Pos + Size;
-                          _Eh ->
-                              %% ?debugVal({_Eh, Pos}),
-                              false
-                      end
-              end,
-    case eleveldb:fold(T, FoldFun, 0, [{verify_checksums, true}]) of
-        false -> false;
-        Pos0 -> true;
-        LastTrimmed when LastTrimmed < Pos0 -> false;
-        _ -> %% LastTrimmed > Pos0, which is a irregular case but ok
-            true
-    end.
+all_trimmed(CsumT, Pos0) ->
+    all_trimmed(CsumT, 0, Pos0).
 
 -spec any_trimmed(table(),
                   pos_integer(),
@@ -248,15 +249,6 @@ build_unwritten_bytes_list([{CurrentOffset, CurrentSize, _Csum}|Rest], LastOffse
 build_unwritten_bytes_list([{CO, CS, _Ck}|Rest], _LastOffset, Acc) ->
     build_unwritten_bytes_list(Rest, CO + CS, Acc).
 
-%% @doc make sure all trimmed chunks are continously chained
-%% TODO: test with EQC
-runthru([], Pos, Pos) -> true;
-runthru([], Pos0, Pos) when Pos0 < Pos -> false;
-runthru([{Offset0, Size0, trimmed}|T], Offset, Pos) when Offset0 =< Offset ->
-    runthru(T, Offset0+Size0, Pos);
-runthru(_L, _O, _P) ->
-    false.
-
 %% @doc If you want to find an overlap among two areas [x, y] and [a,
 %% b] where x < y and a < b; if (a-y)*(b-x) < 0 then there's a
 %% overlap, else, > 0 then there're no overlap. border condition = 0
diff --git a/src/machi_file_proxy.erl b/src/machi_file_proxy.erl
index 480aabd..f6f9bea 100644
--- a/src/machi_file_proxy.erl
+++ b/src/machi_file_proxy.erl
@@ -834,7 +834,7 @@ maybe_gc(Reply, S = #state{fluname=FluName,
                            filename = Filename,
                            eof_position = Eof,
                            csum_table=CsumTable}) ->
-    case machi_csum_table:all_trimmed(CsumTable, Eof) of
+    case machi_csum_table:all_trimmed(CsumTable, ?MINIMUM_OFFSET, Eof) of
         true ->
             lager:debug("GC? Let's do it: ~p.~n", [Filename]),
             %% Before unlinking a file, it should inform
diff --git a/test/machi_csum_table_test.erl b/test/machi_csum_table_test.erl
index 4059de4..f2b7a4f 100644
--- a/test/machi_csum_table_test.erl
+++ b/test/machi_csum_table_test.erl
@@ -113,3 +113,19 @@ smoke3_test() ->
     ok = machi_csum_table:delete(MC).
 
 %% TODO: add quickcheck test here
+
+%% Previous implementation
+-spec all_trimmed2(machi_csum_table:table(),
+                   non_neg_integer(), non_neg_integer()) -> boolean().
+all_trimmed2(CsumT, Left, Right) ->
+    Chunks = machi_csum_table:find(CsumT, Left, Right),
+    runthru(Chunks, Left, Right).
+
+%% @doc make sure all trimmed chunks are continously chained
+%% TODO: test with EQC
+runthru([], Pos, Pos) -> true;
+runthru([], Pos0, Pos) when Pos0 < Pos -> false;
+runthru([{Offset0, Size0, trimmed}|T], Offset, Pos) when Offset0 =< Offset ->
+    runthru(T, Offset0+Size0, Pos);
+runthru(_L, _O, _P) ->
+    false.