diff --git a/libraries/chain/hardfork.d/CORE_1692.hf b/libraries/chain/hardfork.d/CORE_1692.hf
new file mode 100644
index 0000000000..cbbe42c4ae
--- /dev/null
+++ b/libraries/chain/hardfork.d/CORE_1692.hf
@@ -0,0 +1,4 @@
+// bitshares-core issue #1692 validation check of bid_collateral
+#ifndef HARDFORK_CORE_1692_TIME
+#define HARDFORK_CORE_1692_TIME (fc::time_point_sec( 1600000000 ) ) // Sep 2020
+#endif
diff --git a/libraries/chain/market_evaluator.cpp b/libraries/chain/market_evaluator.cpp
index 18ebbe0180..1dd6b7bc6f 100644
--- a/libraries/chain/market_evaluator.cpp
+++ b/libraries/chain/market_evaluator.cpp
@@ -385,13 +385,6 @@ void_result bid_collateral_evaluator::do_evaluate(const bid_collateral_operation
 
    FC_ASSERT( !_bitasset_data->is_prediction_market, "Cannot bid on a prediction market!" );
 
-   if( o.additional_collateral.amount > 0 )
-   {
-      FC_ASSERT( d.get_balance(*_paying_account, _bitasset_data->options.short_backing_asset(d)) >= o.additional_collateral,
-                 "Cannot bid ${c} collateral when payer only has ${b}", ("c", o.additional_collateral.amount)
-                 ("b", d.get_balance(*_paying_account, o.additional_collateral.asset_id(d)).amount) );
-   }
-
    const collateral_bid_index& bids = d.get_index_type<collateral_bid_index>();
    const auto& index = bids.indices().get<by_account>();
    const auto& bid = index.find( boost::make_tuple( o.debt_covered.asset_id, o.bidder ) );
@@ -400,6 +393,22 @@ void_result bid_collateral_evaluator::do_evaluate(const bid_collateral_operation
    else
        FC_ASSERT( o.debt_covered.amount > 0, "Can't find bid to cancel?!");
 
+   if( o.additional_collateral.amount > 0 )
+   {
+      if( _bid && d.head_block_time() >= HARDFORK_CORE_1692_TIME ) // TODO: see if HF check can be removed after HF
+      {
+         asset delta = o.additional_collateral - _bid->get_additional_collateral();
+         FC_ASSERT( d.get_balance(*_paying_account, _bitasset_data->options.short_backing_asset(d)) >= delta,
+                    "Cannot increase bid from ${oc} to ${nc} collateral when payer only has ${b}",
+                    ("oc", _bid->get_additional_collateral().amount)("nc", o.additional_collateral.amount)
+                    ("b", d.get_balance(*_paying_account, o.additional_collateral.asset_id(d)).amount) );
+      } else
+         FC_ASSERT( d.get_balance( *_paying_account,
+                                   _bitasset_data->options.short_backing_asset(d) ) >= o.additional_collateral,
+                    "Cannot bid ${c} collateral when payer only has ${b}", ("c", o.additional_collateral.amount)
+                    ("b", d.get_balance(*_paying_account, o.additional_collateral.asset_id(d)).amount) );
+   }
+
    return void_result();
 } FC_CAPTURE_AND_RETHROW( (o) ) }
 
diff --git a/tests/tests/swan_tests.cpp b/tests/tests/swan_tests.cpp
index 54f233c66a..67cfb200cf 100644
--- a/tests/tests/swan_tests.cpp
+++ b/tests/tests/swan_tests.cpp
@@ -406,6 +406,30 @@ BOOST_AUTO_TEST_CASE( recollateralize )
    }
 }
 
+/** Creates a black swan, bid, adjust bid before/after hf_1692
+ */
+BOOST_AUTO_TEST_CASE( bid_issue_1692 )
+{ try {
+   init_standard_swan( 700 );
+
+   generate_blocks( HARDFORK_CORE_1692_TIME - 30 );
+
+   int64_t b2_balance = get_balance( borrower2(), back() );
+   bid_collateral( borrower2(), back().amount(1000), swan().amount(100) );
+   BOOST_CHECK_EQUAL( get_balance( borrower2(), back() ), b2_balance - 1000 );
+   GRAPHENE_REQUIRE_THROW( bid_collateral( borrower2(), back().amount(b2_balance), swan().amount(200) ),
+                           fc::assert_exception );
+   GRAPHENE_REQUIRE_THROW( bid_collateral( borrower2(), back().amount(b2_balance-999), swan().amount(200) ),
+                           fc::assert_exception );
+
+   generate_blocks( HARDFORK_CORE_1692_TIME + 30 );
+
+   bid_collateral( borrower2(), back().amount(b2_balance-999), swan().amount(200) );
+   BOOST_CHECK_EQUAL( get_balance( borrower2(), back() ), 999 );
+   bid_collateral( borrower2(), back().amount(b2_balance), swan().amount(200) );
+   BOOST_CHECK_EQUAL( get_balance( borrower2(), back() ), 0 );
+} FC_LOG_AND_RETHROW() }
+
 /** Creates a black swan, settles all debts, recovers price feed - asset should be revived
  */
 BOOST_AUTO_TEST_CASE( revive_empty_recovered )