diff --git a/types/btccache.go b/types/btccache.go
index d239ba3b..8023552a 100644
--- a/types/btccache.go
+++ b/types/btccache.go
@@ -32,7 +32,7 @@ func (b *BTCCache) Init(ibs []*IndexedBlock) error {
 		return ErrTooManyEntries
 	}
 	for _, ib := range ibs {
-		if err := b.Add(ib); err != nil {
+		if err := b.add(ib); err != nil {
 			return err
 		}
 	}
@@ -40,11 +40,17 @@ func (b *BTCCache) Init(ibs []*IndexedBlock) error {
 	return b.reverse()
 }
 
+// Add adds a new block to the cache. Thread-safe.
 func (b *BTCCache) Add(ib *IndexedBlock) error {
 	b.Lock()
 	defer b.Unlock()
 
-	if b.Size() >= b.maxEntries {
+	return b.add(ib)
+}
+
+// Thread-unsafe version of Add
+func (b *BTCCache) add(ib *IndexedBlock) error {
+	if b.size() >= b.maxEntries {
 		b.blocks = b.blocks[1:]
 	}
 
@@ -56,7 +62,7 @@ func (b *BTCCache) Tip() (*IndexedBlock, error) {
 	b.RLock()
 	defer b.RUnlock()
 
-	if b.Size() == 0 {
+	if b.size() == 0 {
 		return nil, ErrEmptyCache
 	}
 
@@ -68,7 +74,7 @@ func (b *BTCCache) RemoveLast() error {
 	b.Lock()
 	defer b.Unlock()
 
-	if b.Size() == 0 {
+	if b.size() == 0 {
 		return ErrEmptyCache
 	}
 
@@ -76,17 +82,29 @@ func (b *BTCCache) RemoveLast() error {
 	return nil
 }
 
+// Size returns the size of the cache. Thread-safe.
 func (b *BTCCache) Size() uint64 {
 	b.RLock()
 	defer b.RUnlock()
 
+	return b.size()
+}
+
+// thread-unsafe version of Size
+func (b *BTCCache) size() uint64 {
 	return uint64(len(b.blocks))
 }
 
-func (b *BTCCache) reverse() error {
+// Reverse reverses the order of blocks in cache in place. Thread-safe.
+func (b *BTCCache) Reverse() error {
 	b.Lock()
 	defer b.Unlock()
 
+	return b.reverse()
+}
+
+// thread-unsafe version of Reverse
+func (b *BTCCache) reverse() error {
 	for i, j := 0, len(b.blocks)-1; i < j; i, j = i+1, j-1 {
 		b.blocks[i], b.blocks[j] = b.blocks[j], b.blocks[i]
 	}