diff --git a/storm/array/TSGrowableArray.hpp b/storm/array/TSGrowableArray.hpp
index f03c113..a091103 100644
--- a/storm/array/TSGrowableArray.hpp
+++ b/storm/array/TSGrowableArray.hpp
@@ -18,6 +18,7 @@ class TSGrowableArray : public TSFixedArray<T> {
     void GrowToFit(uint32_t index, int32_t zero);
     T* New(void);
     void Reserve(uint32_t count, int32_t round);
+    uint32_t Reserved() const;
     uint32_t RoundToChunk(uint32_t count, uint32_t chunk);
     void SetCount(uint32_t count);
 };
@@ -112,6 +113,11 @@ void TSGrowableArray<T>::Reserve(uint32_t count, int32_t round) {
     }
 }
 
+template <class T>
+uint32_t TSGrowableArray<T>::Reserved() const {
+    return this->m_alloc - this->m_count;
+}
+
 template <class T>
 uint32_t TSGrowableArray<T>::RoundToChunk(uint32_t count, uint32_t chunk) {
     if (count % chunk) {