diff --git a/src/ircode.c b/src/ircode.c
index 9f71d8e8dd28c..648b954449aa2 100644
--- a/src/ircode.c
+++ b/src/ircode.c
@@ -110,14 +110,14 @@ static void jl_encode_as_indexed_root(jl_ircode_state *s, jl_value_t *v)
         write_uint8(s->s, TAG_RELOC_METHODROOT);
         write_uint64(s->s, rr.key);
     }
-    if (id < 256) {
+    if (id <= UINT8_MAX) {
         write_uint8(s->s, TAG_METHODROOT);
         write_uint8(s->s, id);
     }
     else {
-        assert(id <= UINT16_MAX);
+        assert(id <= UINT32_MAX);
         write_uint8(s->s, TAG_LONG_METHODROOT);
-        write_uint16(s->s, id);
+        write_uint32(s->s, id);
     }
 }
 
@@ -646,11 +646,17 @@ static jl_value_t *jl_decode_value(jl_ircode_state *s) JL_GC_DISABLED
         key = read_uint64(s->s);
         tag = read_uint8(s->s);
         assert(tag == TAG_METHODROOT || tag == TAG_LONG_METHODROOT);
-        return lookup_root(s->method, key, tag == TAG_METHODROOT ? read_uint8(s->s) : read_uint16(s->s));
+        int index = -1;
+        if (tag == TAG_METHODROOT)
+            index = read_uint8(s->s);
+        else if (tag == TAG_LONG_METHODROOT)
+            index = read_uint32(s->s);
+        assert(index >= 0);
+        return lookup_root(s->method, key, index);
     case TAG_METHODROOT:
         return lookup_root(s->method, 0, read_uint8(s->s));
     case TAG_LONG_METHODROOT:
-        return lookup_root(s->method, 0, read_uint16(s->s));
+        return lookup_root(s->method, 0, read_uint32(s->s));
     case TAG_SVEC: JL_FALLTHROUGH; case TAG_LONG_SVEC:
         return jl_decode_value_svec(s, tag);
     case TAG_COMMONSYM: