diff --git a/src/storage/Decomposition.cpp b/src/storage/Decomposition.cpp
index 3e9d2e003..06656b483 100644
--- a/src/storage/Decomposition.cpp
+++ b/src/storage/Decomposition.cpp
@@ -33,7 +33,7 @@ namespace storm {
         }
         
         template <typename BlockType>
-        size_t Decomposition<BlockType>::size() const {
+        std::size_t Decomposition<BlockType>::size() const {
             return blocks.size();
         }
         
diff --git a/src/storage/Decomposition.h b/src/storage/Decomposition.h
index f20d1ede9..6789091d5 100644
--- a/src/storage/Decomposition.h
+++ b/src/storage/Decomposition.h
@@ -2,6 +2,8 @@
 #define STORM_STORAGE_DECOMPOSITION_H_
 
 #include <vector>
+#include <cstdint>
+#include <ostream>
 
 namespace storm {
     namespace storage {
@@ -56,7 +58,7 @@ namespace storm {
              *
              * @return The number of blocks of this decomposition.
              */
-            size_t size() const;
+            std::size_t size() const;
             
             /*!
              * Retrieves an iterator that points to the first block of this decomposition.