diff --git a/c_src/decoder.c b/c_src/decoder.c
index ad3e8d3..f815db2 100644
--- a/c_src/decoder.c
+++ b/c_src/decoder.c
@@ -53,6 +53,7 @@ typedef struct {
     int             is_partial;
     int             return_maps;
     int             use_nil;
+    int             use_undefined;
 
     char*           p;
     unsigned char*  u;
@@ -81,6 +82,7 @@ dec_new(ErlNifEnv* env)
     d->is_partial = 0;
     d->return_maps = 0;
     d->use_nil = 0;
+    d->use_undefined = 0;
 
     d->p = NULL;
     d->u = NULL;
@@ -711,8 +713,16 @@ decode_init(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
             return enif_make_badarg(env);
 #endif
         } else if(enif_compare(val, d->atoms->atom_use_nil) == 0) {
+            /* use_nil and use_undefined are mutually exclusive */
+            if (d->use_undefined)
+                return enif_make_badarg(env);
             d->use_nil = 1;
-        } else {
+        } else if(enif_compare(val, d->atoms->atom_use_undefined) == 0) {
+            if (d->use_nil)
+                return enif_make_badarg(env);
+            d->use_undefined = 1;
+        }
+        else {
             return enif_make_badarg(env);
         }
     }
@@ -783,7 +793,13 @@ decode_iter(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
                             ret = dec_error(d, "invalid_literal");
                             goto done;
                         }
-                        val = d->use_nil ? d->atoms->atom_nil : d->atoms->atom_null;
+                        if(d->use_nil) {
+                            val = d->atoms->atom_nil;
+                        } else if(d->use_undefined) {
+                            val = d->atoms->atom_undefined;
+                        } else {
+                            val = d->atoms->atom_null;
+                        }
                         dec_pop(d, st_value);
                         d->i += 4;
                         break;
diff --git a/c_src/jiffy.c b/c_src/jiffy.c
index 31aa854..c4fe484 100644
--- a/c_src/jiffy.c
+++ b/c_src/jiffy.c
@@ -14,6 +14,7 @@ load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
     st->atom_ok = make_atom(env, "ok");
     st->atom_error = make_atom(env, "error");
     st->atom_null = make_atom(env, "null");
+    st->atom_undefined = make_atom(env, "undefined");
     st->atom_true = make_atom(env, "true");
     st->atom_false = make_atom(env, "false");
     st->atom_bignum = make_atom(env, "bignum");
@@ -28,6 +29,7 @@ load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
     st->atom_return_maps = make_atom(env, "return_maps");
     st->atom_nil = make_atom(env, "nil");
     st->atom_use_nil = make_atom(env, "use_nil");
+    st->atom_use_undefined = make_atom(env, "use_undefined");
 
     // Markers used in encoding
     st->ref_object = make_atom(env, "$object_ref$");
diff --git a/c_src/jiffy.h b/c_src/jiffy.h
index 6d869a5..5dfe8a3 100644
--- a/c_src/jiffy.h
+++ b/c_src/jiffy.h
@@ -16,6 +16,7 @@ typedef struct {
     ERL_NIF_TERM    atom_ok;
     ERL_NIF_TERM    atom_error;
     ERL_NIF_TERM    atom_null;
+    ERL_NIF_TERM    atom_undefined;
     ERL_NIF_TERM    atom_true;
     ERL_NIF_TERM    atom_false;
     ERL_NIF_TERM    atom_bignum;
@@ -30,6 +31,7 @@ typedef struct {
     ERL_NIF_TERM    atom_return_maps;
     ERL_NIF_TERM    atom_nil;
     ERL_NIF_TERM    atom_use_nil;
+    ERL_NIF_TERM    atom_use_undefined;
 
     ERL_NIF_TERM    ref_object;
     ERL_NIF_TERM    ref_array;