diff --git a/base/dict.jl b/base/dict.jl
index 2ea7e983b1c85..d66b93377c7f8 100644
--- a/base/dict.jl
+++ b/base/dict.jl
@@ -247,7 +247,8 @@ push!(t::Associative, p::Pair, q::Pair, r::Pair...) = push!(push!(push!(t, p), q
 
 type ObjectIdDict <: Associative{Any,Any}
     ht::Vector{Any}
-    ObjectIdDict() = new(Vector{Any}(32))
+    ndel::Int
+    ObjectIdDict() = new(Vector{Any}(32), 0)
 
     function ObjectIdDict(itr)
         d = ObjectIdDict()
@@ -266,7 +267,16 @@ end
 
 similar(d::ObjectIdDict) = ObjectIdDict()
 
+function rehash!(t::ObjectIdDict, newsz = length(t.ht))
+    t.ht = ccall(:jl_idtable_rehash, Any, (Any, Csize_t), t.ht, newsz)
+    t
+end
+
 function setindex!(t::ObjectIdDict, v::ANY, k::ANY)
+    if t.ndel >= ((3*length(t.ht))>>2)
+        rehash!(t, max(length(t.ht)>>1, 32))
+        t.ndel = 0
+    end
     t.ht = ccall(:jl_eqtable_put, Array{Any,1}, (Any, Any, Any), t.ht, k, v)
     return t
 end
@@ -274,8 +284,12 @@ end
 get(t::ObjectIdDict, key::ANY, default::ANY) =
     ccall(:jl_eqtable_get, Any, (Any, Any, Any), t.ht, key, default)
 
-pop!(t::ObjectIdDict, key::ANY, default::ANY) =
-    ccall(:jl_eqtable_pop, Any, (Any, Any, Any), t.ht, key, default)
+function pop!(t::ObjectIdDict, key::ANY, default::ANY)
+    val = ccall(:jl_eqtable_pop, Any, (Any, Any, Any), t.ht, key, default)
+    # TODO: this can underestimate `ndel`
+    val === default || (t.ndel += 1)
+    return val
+end
 
 function pop!(t::ObjectIdDict, key::ANY)
     val = pop!(t, key, secret_table_token)
@@ -283,11 +297,11 @@ function pop!(t::ObjectIdDict, key::ANY)
 end
 
 function delete!(t::ObjectIdDict, key::ANY)
-    ccall(:jl_eqtable_pop, Any, (Any, Any), t.ht, key)
+    pop!(t, key, secret_table_token)
     t
 end
 
-empty!(t::ObjectIdDict) = (t.ht = Vector{Any}(length(t.ht)); t)
+empty!(t::ObjectIdDict) = (t.ht = Vector{Any}(length(t.ht)); t.ndel = 0; t)
 
 _oidd_nextind(a, i) = reinterpret(Int,ccall(:jl_eqtable_nextind, Csize_t, (Any, Csize_t), a, i))
 
diff --git a/src/dump.c b/src/dump.c
index 7157d89bb5a36..d46fb1b624d7a 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -1815,7 +1815,7 @@ static void jl_reinit_item(jl_value_t *v, int how, arraylist_t *tracee_list)
             case 1: { // rehash ObjectIdDict
                 jl_array_t **a = (jl_array_t**)v;
                 // Assume *a don't need a write barrier
-                jl_idtable_rehash(a, jl_array_len(*a));
+                *a = jl_idtable_rehash(*a, jl_array_len(*a));
                 jl_gc_wb(v, *a);
                 break;
             }
diff --git a/src/julia_internal.h b/src/julia_internal.h
index 2c7105b62e53c..8346c247e5808 100644
--- a/src/julia_internal.h
+++ b/src/julia_internal.h
@@ -425,7 +425,7 @@ int32_t jl_get_llvm_gv(jl_value_t *p);
 int32_t jl_assign_functionID(/*llvm::Function*/void *function);
 // the first argument to jl_idtable_rehash is used to return a value
 // make sure it is rooted if it is used after the function returns
-void jl_idtable_rehash(jl_array_t **pa, size_t newsz);
+JL_DLLEXPORT jl_array_t *jl_idtable_rehash(jl_array_t *a, size_t newsz);
 
 JL_DLLEXPORT jl_methtable_t *jl_new_method_table(jl_sym_t *name, jl_module_t *module);
 jl_lambda_info_t *jl_get_specialization1(jl_tupletype_t *types);
diff --git a/src/table.c b/src/table.c
index 5bed49efbfe26..37738f9816d71 100644
--- a/src/table.c
+++ b/src/table.c
@@ -10,13 +10,13 @@
 
 static void **jl_table_lookup_bp(jl_array_t **pa, void *key);
 
-void jl_idtable_rehash(jl_array_t **pa, size_t newsz)
+JL_DLLEXPORT jl_array_t *jl_idtable_rehash(jl_array_t *a, size_t newsz)
 {
     // Assume *pa don't need a write barrier
     // pa doesn't have to be a GC slot but *pa needs to be rooted
-    size_t sz = jl_array_len(*pa);
+    size_t sz = jl_array_len(a);
     size_t i;
-    void **ol = (void**)(*pa)->data;
+    void **ol = (void**)a->data;
     jl_array_t *newa = jl_alloc_vec_any(newsz);
     // keep the original array in the original slot since we need `ol`
     // to be valid in the loop below.
@@ -25,16 +25,16 @@ void jl_idtable_rehash(jl_array_t **pa, size_t newsz)
         if (ol[i+1] != NULL) {
             (*jl_table_lookup_bp(&newa, ol[i])) = ol[i+1];
             jl_gc_wb(newa, ol[i+1]);
-             // it is however necessary here because allocation
+            // it is however necessary here because allocation
             // can (and will) occur in a recursive call inside table_lookup_bp
         }
     }
-    *pa = newa;
     // we do not check the write barrier here
     // because pa always points to a C stack location
     // (see jl_eqtable_put and jl_finalize_deserializer)
     // it should be changed if this assumption no longer holds
     JL_GC_POP();
+    return newa;
 }
 
 static void **jl_table_lookup_bp(jl_array_t **pa, void *key)
@@ -44,6 +44,7 @@ static void **jl_table_lookup_bp(jl_array_t **pa, void *key)
     jl_array_t *a = *pa;
     size_t orig, index, iter;
     size_t newsz, sz = hash_size(a);
+    assert(sz >= 1);
     size_t maxprobe = max_probe(sz);
     void **tab = (void**)a->data;
 
@@ -81,7 +82,7 @@ static void **jl_table_lookup_bp(jl_array_t **pa, void *key)
         newsz = HT_N_INLINE;
     else
         newsz = sz<<2;
-    jl_idtable_rehash(pa, newsz);
+    *pa = jl_idtable_rehash(*pa, newsz);
 
     a = *pa;
     tab = (void**)a->data;
@@ -98,6 +99,7 @@ static void **jl_table_lookup_bp(jl_array_t **pa, void *key)
 static void **jl_table_peek_bp(jl_array_t *a, void *key)
 {
     size_t sz = hash_size(a);
+    assert(sz >= 1);
     size_t maxprobe = max_probe(sz);
     void **tab = (void**)a->data;
     uint_t hv = keyhash((jl_value_t*)key);