diff --git a/src/staticdata.c b/src/staticdata.c
index 9b599c0ff1a7f..5a67ebd7eb313 100644
--- a/src/staticdata.c
+++ b/src/staticdata.c
@@ -1425,22 +1425,25 @@ static void jl_finalize_deserializer(jl_serializer_state *s) JL_GC_DISABLED
 
 
 
-// --- helper functions ---
-
-// remove cached types not referenced in the stream
-static int keep_type_cache_entry(jl_value_t *ti)
+static void jl_scan_type_cache_gv(jl_serializer_state *s, jl_svec_t *cache)
 {
-    if (ptrhash_get(&backref_table, ti) != HT_NOTFOUND || jl_get_llvm_gv(native_functions, ti) != 0)
-        return 1;
-    if (jl_is_datatype(ti)) {
-        jl_value_t *singleton = ((jl_datatype_t*)ti)->instance;
-        if (singleton && (ptrhash_get(&backref_table, singleton) != HT_NOTFOUND ||
-                    jl_get_llvm_gv(native_functions, singleton) != 0))
-            return 1;
-    }
-    return 0;
+    size_t l = jl_svec_len(cache), i;
+    for (i = 0; i < l; i++) {
+        jl_value_t *ti = jl_svecref(cache, i);
+        if (ti == NULL || ti == jl_nothing)
+            continue;
+        if (jl_get_llvm_gv(native_functions, ti)) {
+            jl_serialize_value(s, ti);
+        }
+        else if (jl_is_datatype(ti)) {
+            jl_value_t *singleton = ((jl_datatype_t*)ti)->instance;
+            if (singleton && jl_get_llvm_gv(native_functions, singleton))
+                jl_serialize_value(s, ti);
+        }
+    }
 }
 
+// remove cached types not referenced in the stream
 static void jl_prune_type_cache_hash(jl_svec_t *cache)
 {
     size_t l = jl_svec_len(cache), i;
@@ -1448,7 +1451,7 @@ static void jl_prune_type_cache_hash(jl_svec_t *cache)
         jl_value_t *ti = jl_svecref(cache, i);
         if (ti == NULL || ti == jl_nothing)
             continue;
-        if (!keep_type_cache_entry(ti))
+        if (ptrhash_get(&backref_table, ti) == HT_NOTFOUND)
             jl_svecset(cache, i, jl_nothing);
     }
 }
@@ -1460,7 +1463,7 @@ static void jl_prune_type_cache_linear(jl_svec_t *cache)
         jl_value_t *ti = jl_svecref(cache, i);
         if (ti == NULL)
             break;
-        if (keep_type_cache_entry(ti))
+        if (ptrhash_get(&backref_table, ti) != HT_NOTFOUND)
             jl_svecset(cache, ins++, ti);
     }
     if (i > ins) {
@@ -1526,14 +1529,28 @@ static void jl_save_system_image_to_stream(ios_t *f) JL_GC_DISABLED
             jl_value_t *tag = *tags[i];
             jl_serialize_value(&s, tag);
         }
-        // prune unused entries from built-in type caches
+        // step 1.1: check for values only found in the generated code
+        arraylist_t typenames;
+        arraylist_new(&typenames, 0);
         for (i = 0; i < backref_table.size; i += 2) {
             jl_typename_t *tn = (jl_typename_t*)backref_table.table[i];
             if (tn == HT_NOTFOUND || !jl_is_typename(tn))
                 continue;
+            arraylist_push(&typenames, tn);
+        }
+        for (i = 0; i < typenames.len; i++) {
+            jl_typename_t *tn = (jl_typename_t*)typenames.items[i];
+            jl_scan_type_cache_gv(&s, tn->cache);
+            jl_scan_type_cache_gv(&s, tn->linearcache);
+        }
+        // step 1.2: prune (garbage collect) some special weak references from
+        // built-in type caches
+        for (i = 0; i < typenames.len; i++) {
+            jl_typename_t *tn = (jl_typename_t*)typenames.items[i];
             jl_prune_type_cache_hash(tn->cache);
             jl_prune_type_cache_linear(tn->linearcache);
         }
+        arraylist_free(&typenames);
     }
 
     { // step 2: build all the sysimg sections