diff --git a/src/monitor.cc b/src/monitor.cc
index caaa116..b641160 100644
--- a/src/monitor.cc
+++ b/src/monitor.cc
@@ -800,12 +800,15 @@
                                 const char*& source_file, uint32_t& line_number) const {
   // If method is null, location is unknown
   if (method == NULL) {
-    source_file = "unknown";
+    source_file = "";
     line_number = 0;
     return;
   }
   MethodHelper mh(method);
   source_file = mh.GetDeclaringClassSourceFile();
+  if (source_file == NULL) {
+    source_file = "";
+  }
   line_number = mh.GetLineNumFromNativePC(pc);
 }
 
diff --git a/src/object_utils.h b/src/object_utils.h
index 0412858..3af7007 100644
--- a/src/object_utils.h
+++ b/src/object_utils.h
@@ -169,11 +169,8 @@
     std::string descriptor(GetDescriptor());
     const DexFile& dex_file = GetDexFile();
     const DexFile::ClassDef* dex_class_def = dex_file.FindClassDef(descriptor);
-    if (dex_class_def == NULL) {
-      return NULL;
-    } else {
-      return dex_file.GetSourceFile(*dex_class_def);
-    }
+    CHECK(dex_class_def != NULL);
+    return dex_file.GetSourceFile(*dex_class_def);
   }
 
   std::string GetLocation() {
@@ -477,11 +474,8 @@
     const char* descriptor = GetDeclaringClassDescriptor();
     const DexFile& dex_file = GetDexFile();
     const DexFile::ClassDef* dex_class_def = dex_file.FindClassDef(descriptor);
-    if (dex_class_def == NULL) {
-      return NULL;
-    } else {
-      return dex_file.GetSourceFile(*dex_class_def);
-    }
+    CHECK(dex_class_def != NULL);
+    return dex_file.GetSourceFile(*dex_class_def);
   }
   bool IsStatic() {
     return method_->IsStatic();