diff --git a/Android.bp b/Android.bp
index f565732..5b2e600 100644
--- a/Android.bp
+++ b/Android.bp
@@ -31,6 +31,7 @@
         "libavb",
         "libbootloader_message",
         "libdm",
+        "libext2_uuid",
         "libfec",
         "libfec_rs",
         "libfs_avb",
diff --git a/Checkpoint.cpp b/Checkpoint.cpp
index 362c823..e5ef4a2 100644
--- a/Checkpoint.cpp
+++ b/Checkpoint.cpp
@@ -144,9 +144,15 @@
 namespace {
 
 volatile bool isCheckpointing = false;
+
+// Protects isCheckpointing and code that makes decisions based on status of
+// isCheckpointing
+std::mutex isCheckpointingLock;
 }
 
 Status cp_commitChanges() {
+    std::lock_guard<std::mutex> lock(isCheckpointingLock);
+
     if (!isCheckpointing) {
         return Status::ok();
     }
@@ -257,10 +263,16 @@
 }
 
 bool cp_needsCheckpoint() {
+    // Make sure we only return true during boot. See b/138952436 for discussion
+    static bool called_once = false;
+    if (called_once) return isCheckpointing;
+    called_once = true;
+
     bool ret;
     std::string content;
     sp<IBootControl> module = IBootControl::getService();
 
+    std::lock_guard<std::mutex> lock(isCheckpointingLock);
     if (isCheckpointing) return isCheckpointing;
 
     if (module && module->isSlotMarkedSuccessful(module->getCurrentSlot()) == BoolResult::FALSE) {
@@ -330,6 +342,7 @@
 }  // namespace
 
 Status cp_prepareCheckpoint() {
+    std::lock_guard<std::mutex> lock(isCheckpointingLock);
     if (!isCheckpointing) {
         return Status::ok();
     }