diff --git a/include/rapidjson/schema.h b/include/rapidjson/schema.h
index 288b93d..420db62 100644
--- a/include/rapidjson/schema.h
+++ b/include/rapidjson/schema.h
@@ -1366,6 +1366,9 @@ public:
                     new (schemaMap_.template Push<SchemaEntry>()) SchemaEntry(refEntry->source, const_cast<SchemaType*>(s), false, allocator_);
                 }
             }
+            else if (refEntry->schema)
+                *refEntry->schema = SchemaType::GetTypeless();
+            
             refEntry->~SchemaRefEntry();
         }
 
diff --git a/test/unittest/schematest.cpp b/test/unittest/schematest.cpp
index 6a8b685..4780516 100644
--- a/test/unittest/schematest.cpp
+++ b/test/unittest/schematest.cpp
@@ -1308,6 +1308,14 @@ TEST(SchemaValidator, Issue608) {
     INVALIDATE(s, "{\"a\" : null, \"a\" : null}", "", "required", "");
 }
 
+// Fail to resolve $ref in allOf causes crash in SchemaValidator::StartObject()
+TEST(SchemaValidator, Issue728_AllOfRef) {
+    Document sd;
+    sd.Parse("{\"allOf\": [{\"$ref\": \"#/abc\"}]}");
+    SchemaDocument s(sd);
+    VALIDATE(s, "{\"key1\": \"abc\", \"key2\": \"def\"}", true);
+}
+
 #ifdef __clang__
 RAPIDJSON_DIAG_POP
 #endif