diff --git a/src/storm-gspn/parser/GreatSpnEditorProjectParser.cpp b/src/storm-gspn/parser/GreatSpnEditorProjectParser.cpp
index 2ab73ac91..ae17ca59b 100644
--- a/src/storm-gspn/parser/GreatSpnEditorProjectParser.cpp
+++ b/src/storm-gspn/parser/GreatSpnEditorProjectParser.cpp
@@ -212,7 +212,7 @@ namespace storm {
                     STORM_PRINT_AND_LOG("unknown child (node=" + storm::adapters::XMLtoString(node->getNodeName()) + "): " + name + "\n");
                 }
             }
-            builder.addPlace(-1, initialTokens, placeName);
+            builder.addPlace(boost::none, initialTokens, placeName);
         }
 
         bool ignoreTransitionAttribute(std::string const& name) {
diff --git a/src/storm-gspn/parser/PnmlParser.cpp b/src/storm-gspn/parser/PnmlParser.cpp
index 71757defc..189e34266 100644
--- a/src/storm-gspn/parser/PnmlParser.cpp
+++ b/src/storm-gspn/parser/PnmlParser.cpp
@@ -104,7 +104,7 @@ namespace storm {
             std::string placeName;
             // the first entry is false if the corresponding information was not found in the pnml file
             std::pair<bool, uint_fast64_t> numberOfInitialTokens(false, defaultNumberOfInitialTokens);
-            std::pair<bool, int_fast64_t> capacity(false, defaultCapacity);
+            std::pair<bool, boost::optional<uint64_t>> capacity(false, boost::none);
 
             // traverse attributes
             for (uint_fast64_t i = 0; i < node->getAttributes()->getLength(); ++i) {
@@ -150,10 +150,9 @@ namespace storm {
             }
             if (!capacity.first) {
                 // no information about the capacity is found
-                // use default capacity
                 STORM_PRINT_AND_LOG("unknown capacity (place=" + placeName + ")\n");
             }
-            builder.addPlace(capacity.first ? capacity.second : -1, numberOfInitialTokens.first ? numberOfInitialTokens.second : 0, placeName);
+            builder.addPlace(capacity.second, numberOfInitialTokens.first ? numberOfInitialTokens.second : 0, placeName);
         }
 
         void PnmlParser::traverseTransition(xercesc::DOMNode const* const node) {
diff --git a/src/storm-gspn/storage/gspn/GspnBuilder.cpp b/src/storm-gspn/storage/gspn/GspnBuilder.cpp
index 5303a89c6..e273768ea 100644
--- a/src/storm-gspn/storage/gspn/GspnBuilder.cpp
+++ b/src/storm-gspn/storage/gspn/GspnBuilder.cpp
@@ -13,7 +13,7 @@ namespace storm {
             gspnName = name;
         }
         
-        uint_fast64_t GspnBuilder::addPlace(int_fast64_t const& capacity, uint_fast64_t const& initialTokens, std::string const& name) {
+        uint_fast64_t GspnBuilder::addPlace(boost::optional<uint64_t> capacity, uint_fast64_t const& initialTokens, std::string const& name) {
             auto newId = places.size();
             auto place = storm::gspn::Place(newId);
             place.setCapacity(capacity);
diff --git a/src/storm-gspn/storage/gspn/GspnBuilder.h b/src/storm-gspn/storage/gspn/GspnBuilder.h
index 79fb2e712..a9a99699f 100644
--- a/src/storm-gspn/storage/gspn/GspnBuilder.h
+++ b/src/storm-gspn/storage/gspn/GspnBuilder.h
@@ -25,7 +25,7 @@ namespace storm {
              *                 A capacity of -1 indicates an unbounded place.
              * @param initialTokens The number of inital tokens in the place.
              */
-            uint_fast64_t addPlace(int_fast64_t const& capacity = 1, uint_fast64_t const& initialTokens = 0, std::string const& name = "");
+            uint_fast64_t addPlace(boost::optional<uint64_t> capacity = 1, uint_fast64_t const& initialTokens = 0, std::string const& name = "");
             
             void setPlaceLayoutInfo(uint64_t placeId, LayoutInfo const& layoutInfo);
 
diff --git a/src/storm-gspn/storage/gspn/Place.cpp b/src/storm-gspn/storage/gspn/Place.cpp
index a78b7c585..d60ace5f6 100644
--- a/src/storm-gspn/storage/gspn/Place.cpp
+++ b/src/storm-gspn/storage/gspn/Place.cpp
@@ -29,7 +29,7 @@ namespace storm {
             return this->numberOfInitialTokens;
         }
 
-        void Place::setCapacity(uint64_t cap) {
+        void Place::setCapacity(boost::optional<uint64_t> cap) {
             this->capacity = cap;
         }
 
diff --git a/src/storm-gspn/storage/gspn/Place.h b/src/storm-gspn/storage/gspn/Place.h
index e995f6a93..55c9da6fb 100644
--- a/src/storm-gspn/storage/gspn/Place.h
+++ b/src/storm-gspn/storage/gspn/Place.h
@@ -54,9 +54,9 @@ namespace storm {
              * Sets the capacity of tokens of this place.
              *
              * @param capacity The capacity of this place. A non-negative number represents the capacity.
-             *                 The value -1 indicates that the capacity is not set.
+             *                 boost::none indicates that the flag is not set.
              */
-            void setCapacity(uint64_t capacity);
+            void setCapacity(boost::optional<uint64_t> capacity);
 
             /*!
              * Returns the capacity of tokens of this place.