diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2a4f04e..9784fe6e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.5.4
+ - Important correctness fix when storing very many equally sized objects
+that may get GC'ed while storing is in progress! (#603)
+
 ## 0.5.3
  - Bugfix for `<: Function` structs
 
diff --git a/Project.toml b/Project.toml
index 9361c70c..caaac3c2 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "JLD2"
 uuid = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
-version = "0.5.3"
+version = "0.5.4"
 
 [deps]
 FileIO = "5789e2e9-d7fb-5bc7-8068-2c6fae9b9549"
diff --git a/src/JLD2.jl b/src/JLD2.jl
index b76b1780..079d00c2 100644
--- a/src/JLD2.jl
+++ b/src/JLD2.jl
@@ -113,7 +113,7 @@ mutable struct JLDFile{T<:IO}
     disable_commit::Bool
     datatype_locations::OrderedDict{RelOffset,CommittedDatatype}
     datatypes::Vector{H5Datatype}
-    datatype_wsession::JLDWriteSession{Dict{UInt,RelOffset}}
+    datatype_wsession::JLDWriteSession{Dict{UInt,Tuple{RelOffset,WeakRef}}}
     typemap::Dict{String, Any}
     jlh5type::IdDict{Any,Any}
     h5jltype::IdDict{Any,Any}
diff --git a/src/types.jl b/src/types.jl
index c9e7ad77..04905020 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -112,25 +112,25 @@ A `JLDWriteSession` keeps track of references to serialized objects. If `T` is a
 written dataset. If it is `Union{}`, then references are not tracked, and objects
 referenced multiple times are written multiple times.
 """
-struct JLDWriteSession{T<:Union{Dict{UInt,RelOffset},Union{}}}
+struct JLDWriteSession{T<:Union{Dict{UInt,Tuple{RelOffset,WeakRef}},Union{}}}
     h5offset::T
-    JLDWriteSession{T}() where T = new()
-    JLDWriteSession{T}(h5offset, objects) where T = new(h5offset)
+    JLDWriteSession{T}() where T = new{T}()
+    JLDWriteSession(h5offset::T) where T = new{T}(h5offset)
 end
-JLDWriteSession() = JLDWriteSession{Dict{UInt,RelOffset}}(Dict{UInt,RelOffset}(), Any[])
+JLDWriteSession() = JLDWriteSession(Dict{UInt,Tuple{RelOffset,WeakRef}}())
 track!(::JLDWriteSession{Union{}}, args...) = nothing
 function track!(s::JLDWriteSession, data, offset::RelOffset)
     if ismutabletype(typeof(data))
-        s.h5offset[objectid(data)] = offset
+        s.h5offset[objectid(data)] = (offset, WeakRef(data))
     end
     nothing
 end
-get_tracked(wsession::JLDWriteSession{Union{}}, data) = UNDEFINED_ADDRESS
+get_tracked(::JLDWriteSession{Union{}}, data) = UNDEFINED_ADDRESS
 function get_tracked(wsession::JLDWriteSession, data)
-    if ismutabletype(typeof(data))
-        return get(wsession.h5offset, objectid(data), UNDEFINED_ADDRESS)
-    end
-    return UNDEFINED_ADDRESS
+    !ismutabletype(typeof(data)) && return UNDEFINED_ADDRESS
+    offset, wref = get(wsession.h5offset, objectid(data), (UNDEFINED_ADDRESS, WeakRef(nothing)))
+    isnothing(wref.value) && return UNDEFINED_ADDRESS
+    return offset
 end
 """
     GlobalHeap
diff --git a/test/loadsave.jl b/test/loadsave.jl
index 30329062..4684601b 100644
--- a/test/loadsave.jl
+++ b/test/loadsave.jl
@@ -801,3 +801,40 @@ end
     loaded_foo = load(tempfile, "foo")
     @test loaded_foo isa Foo601
 end
+
+
+@testset "Issue #603 - reused objectids" begin
+    fn = joinpath(mktempdir(), "issue603_reused_objectids.jld2")
+
+    function create_large_dict(levels::Int, items_per_level::Int, item_size::Int)
+        # Create a nested dictionary with the specified number of levels
+        function create_nested_dict(current_level, max_level)
+            if current_level > max_level
+                return Dict("x" => rand(Int, item_size))
+            else
+                return Dict(
+                    string(i) => create_nested_dict(current_level + 1, max_level)
+                    for i in 1:items_per_level
+                )
+            end
+        end
+        # Create the top-level dictionary
+        return create_nested_dict(1, levels)
+    end
+
+    obj = create_large_dict(3, 30, 1);
+    jldsave(fn; obj)
+    res = load(fn, "obj")
+    function recursive_test(obj, res)
+        @test length(keys(obj)) == length(keys(res))
+        for (k, v) in obj
+            @test haskey(res, k)
+            if isa(v, Dict)
+                recursive_test(v, res[k])
+            else
+                @test v == res[k]
+            end
+        end
+    end
+    recursive_test(obj, res)
+end
\ No newline at end of file