diff --git a/core/src/main/java/org/teavm/runtime/GC.java b/core/src/main/java/org/teavm/runtime/GC.java
index f33172cd9..0d670f589 100644
--- a/core/src/main/java/org/teavm/runtime/GC.java
+++ b/core/src/main/java/org/teavm/runtime/GC.java
@@ -438,7 +438,9 @@ public final class GC {
                 hasObjectsFromYoungGen |= enqueueMark(object.object);
             }
         }
-        if (object.next == null && object.object != null) {
+        if (object.next != null) {
+            hasObjectsFromYoungGen |= enqueueMark(object.next);
+        } else if (object.object != null) {
             object.next = firstWeakReference;
             firstWeakReference = object;
         }
@@ -448,9 +450,8 @@ public final class GC {
     private static boolean markReferenceQueue(RuntimeReferenceQueue object) {
         RuntimeReference reference = object.first;
         boolean hasObjectsFromYoungGen = false;
-        while (reference != null) {
+        if (reference != null) {
             hasObjectsFromYoungGen |= enqueueMark(reference);
-            reference = reference.next;
         }
         return hasObjectsFromYoungGen;
     }
@@ -519,14 +520,22 @@ public final class GC {
                         queue.first = reference;
                     } else {
                         queue.last.next = reference;
+                        makeInvalid(queue.last);
                     }
                     queue.last = reference;
+                    makeInvalid(queue);
                 }
             }
             reference = next;
         }
     }
 
+    private static void makeInvalid(RuntimeObject object) {
+        long offset = object.toAddress().toLong() - heapAddress().toLong();
+        Address cardTableItem = cardTable().add(offset / regionSize());
+        cardTableItem.putByte((byte) (cardTableItem.getByte() & ~CARD_VALID));
+    }
+
     private static void sweep() {
         MemoryTrace.sweepStarted();
 
diff --git a/core/src/main/resources/org/teavm/backend/c/heaptrace.c b/core/src/main/resources/org/teavm/backend/c/heaptrace.c
index fcf8107d9..6037870dc 100644
--- a/core/src/main/resources/org/teavm/backend/c/heaptrace.c
+++ b/core/src/main/resources/org/teavm/backend/c/heaptrace.c
@@ -4,6 +4,7 @@
 #include "definitions.h"
 #include "memory.h"
 #include "time.h"
+#include "references.h"
 #include <string.h>
 #include <stdint.h>
 #include <inttypes.h>
@@ -363,9 +364,14 @@ FILE* teavm_gc_openDumpFile(wchar_t* name) {
                     while (cls != NULL) {
                         int32_t kind = (cls->flags >> 7) & 7;
                         if (kind == 1) {
-
+                            TeaVM_Reference* reference = (TeaVM_Reference*) obj;
+                            teavm_verify(reference->next);
+                            teavm_verify(reference->object);
+                            teavm_verify(reference->queue);
                         } else if (kind == 2) {
-
+                            TeaVM_ReferenceQueue* queue = (TeaVM_ReferenceQueue*) obj;
+                            teavm_verify(queue->first);
+                            teavm_verify(queue->last);
                         } else {
                             int16_t* layout = cls->layout;
                             if (layout != NULL) {