diff --git a/base/runtime_internals.jl b/base/runtime_internals.jl
index 4471638f49ba1c..0765960c97ab35 100644
--- a/base/runtime_internals.jl
+++ b/base/runtime_internals.jl
@@ -976,7 +976,7 @@ function morespecific!(m::Method)
     # check that all Methods in this table are morespecific than m
     # so we might avoid disabling a table that might get used for more than just subsets of m
     all(m2 -> m === m2 || morespecific(m2, m), MethodList(mt)) || error("unsupported Method to disable")
-    setfield!(mt, nfields(mt), 0x1)
+    setfield!(mt, :frozen, 0x1, :monotonic)
 end
 
 """
diff --git a/src/datatype.c b/src/datatype.c
index c78b00fdd22456..44dedce8a3c02d 100644
--- a/src/datatype.c
+++ b/src/datatype.c
@@ -54,7 +54,7 @@ JL_DLLEXPORT jl_methtable_t *jl_new_method_table(jl_sym_t *name, jl_module_t *mo
     mt->backedges = NULL;
     JL_MUTEX_INIT(&mt->writelock, "methodtable->writelock");
     mt->offs = 0;
-    mt->frozen = 0;
+    jl_atomic_store_relaxed(&mt->frozen, 0);
     return mt;
 }
 
diff --git a/src/gf.c b/src/gf.c
index abdda56730580a..fcf25fb40dd392 100644
--- a/src/gf.c
+++ b/src/gf.c
@@ -331,7 +331,7 @@ jl_datatype_t *jl_mk_builtin_func(jl_datatype_t *dt, const char *name, jl_fptr_a
             (jl_value_t*)mi, 1, ~(size_t)0);
     jl_typemap_insert(&mt->cache, (jl_value_t*)mt, newentry, 0);
 
-    mt->frozen = 1;
+    jl_atomic_store_relaxed(&mt->frozen, 1);
     JL_GC_POP();
     return dt;
 }
@@ -772,7 +772,7 @@ static int reset_mt_caches(jl_methtable_t *mt, void *env)
 {
     // removes all method caches
     // this might not be entirely safe (GC or MT), thus we only do it very early in bootstrapping
-    if (!mt->frozen) { // make sure not to reset frozen functions
+    if (!jl_atomic_load_relaxed(&mt->frozen)) { // make sure not to reset frozen functions
         jl_atomic_store_release(&mt->leafcache, (jl_genericmemory_t*)jl_an_empty_memory_any);
         jl_atomic_store_release(&mt->cache, jl_nothing);
     }
diff --git a/src/jltypes.c b/src/jltypes.c
index 11f1d11a14edc4..8b6e50dffdb8e2 100644
--- a/src/jltypes.c
+++ b/src/jltypes.c
@@ -3038,9 +3038,9 @@ void jl_init_types(void) JL_GC_DISABLED
     jl_methtable_type->name->names = jl_perm_symsvec(11, "name", "defs",
                                                      "leafcache", "cache", "max_args",
                                                      "module", "backedges",
-                                                     "", "", "offs", "");
+                                                     "", "", "offs", "frozen");
     const static uint32_t methtable_constfields[1] = { 0x00000020 }; // (1<<5);
-    const static uint32_t methtable_atomicfields[1] = { 0x0000001e }; // (1<<1)|(1<<2)|(1<<3)|(1<<4);
+    const static uint32_t methtable_atomicfields[1] = { 0x00000041e }; // (1<<1)|(1<<2)|(1<<3)|(1<<4)|(1<<10);
     jl_methtable_type->name->constfields = methtable_constfields;
     jl_methtable_type->name->atomicfields = methtable_atomicfields;
     jl_precompute_memoized_dt(jl_methtable_type, 1);
diff --git a/src/julia.h b/src/julia.h
index 7bb5f31eda7088..837724cc5253d2 100644
--- a/src/julia.h
+++ b/src/julia.h
@@ -791,7 +791,7 @@ typedef struct _jl_methtable_t {
     jl_array_t *backedges; // (sig, caller::MethodInstance) pairs
     jl_mutex_t writelock;
     uint8_t offs;  // 0, or 1 to skip splitting typemap on first (function) argument
-    uint8_t frozen; // whether this accepts adding new methods
+    _Atomic(uint8_t) frozen; // whether this accepts adding new methods
 } jl_methtable_t;
 
 typedef struct {
diff --git a/src/staticdata.c b/src/staticdata.c
index af4527cbc143f3..a432dd0ad3cdee 100644
--- a/src/staticdata.c
+++ b/src/staticdata.c
@@ -975,7 +975,7 @@ static void jl_insert_into_serialization_queue(jl_serializer_state *s, jl_value_
             }
             else if (jl_typetagis(v, jl_typename_type)) {
                 jl_typename_t *tn = (jl_typename_t*)v;
-                if (tn->mt != NULL && !tn->mt->frozen) {
+                if (tn->mt != NULL && !jl_atomic_load_relaxed(&tn->mt->frozen)) {
                     jl_methtable_t * new_methtable = (jl_methtable_t *)ptrhash_get(&new_methtables, tn->mt);
                     if (new_methtable != HT_NOTFOUND)
                         record_field_change((jl_value_t **)&tn->mt, (jl_value_t*)new_methtable);