diff --git a/src/dex_verifier.h b/src/dex_verifier.h
index a703cbc..3a7e3d2 100644
--- a/src/dex_verifier.h
+++ b/src/dex_verifier.h
@@ -1225,7 +1225,7 @@
  public:
   PcToReferenceMap(Method* m) {
     data_ = down_cast<ByteArray*>(m->GetGcMap());
-    CHECK(data_ != NULL);
+    CHECK(data_ != NULL) << PrettyMethod(m);
     // Check the size of the table agrees with the number of entries
     size_t data_size = data_->GetLength() - 4;
     DCHECK_EQ(EntryWidth() * NumEntries(), data_size);
diff --git a/src/thread.cc b/src/thread.cc
index e3596d3..b8df84f 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -510,8 +510,12 @@
     Method* m = frame.GetMethod();
     Class* c = m->GetDeclaringClass();
     ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
-    const DexFile& dex_file = class_linker->FindDexFile(c->GetDexCache());
-    int line_number = dex_file.GetLineNumFromPC(m, m->ToDexPC(pc));
+    const DexCache* dex_cache = c->GetDexCache();
+    int line_number = -1;
+    if (dex_cache != NULL) {  // be tolerant of bad input
+      const DexFile& dex_file = class_linker->FindDexFile(dex_cache);
+      line_number = dex_file.GetLineNumFromPC(m, m->ToDexPC(pc));
+    }
     if (line_number == last_line_number && last_method == m) {
       repetition_count++;
     } else {