diff --git a/src/storm-parsers/parser/ConstantDataType.cpp b/src/storm-parsers/parser/ConstantDataType.cpp
new file mode 100644
index 000000000..52ab7c9d9
--- /dev/null
+++ b/src/storm-parsers/parser/ConstantDataType.cpp
@@ -0,0 +1,14 @@
+#include "ConstantDataType.h"
+
+namespace storm {
+    namespace parser {
+        std::ostream& operator<<(std::ostream& out, ConstantDataType const& constantDataType) {
+          switch(constantDataType) {
+            case storm::parser::ConstantDataType::Bool: out << "Bool"; break;
+            case storm::parser::ConstantDataType::Integer: out << "Integer"; break;
+            case storm::parser::ConstantDataType::Rational: out << "Rational"; break;
+          }
+          return out;
+        }
+    }
+}
diff --git a/src/storm-parsers/parser/ConstantDataType.h b/src/storm-parsers/parser/ConstantDataType.h
new file mode 100644
index 000000000..b8e7aa975
--- /dev/null
+++ b/src/storm-parsers/parser/ConstantDataType.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <sstream>
+
+namespace storm {
+    namespace parser {
+
+        enum class ConstantDataType {
+            Bool, Integer, Rational
+        };
+
+        std::ostream& operator<<(std::ostream& out, ConstantDataType const& constantDataType);
+    }
+}
diff --git a/src/storm-parsers/parser/FormulaParserGrammar.h b/src/storm-parsers/parser/FormulaParserGrammar.h
index 75903d04a..9ea0e5355 100644
--- a/src/storm-parsers/parser/FormulaParserGrammar.h
+++ b/src/storm-parsers/parser/FormulaParserGrammar.h
@@ -10,6 +10,7 @@
 #include "storm/storage/jani/Property.h"
 #include "storm/logic/Formulas.h"
 #include "storm-parsers/parser/ExpressionParser.h"
+#include "storm-parsers/parser/ConstantDataType.h"
 
 #include "storm/modelchecker/results/FilterType.h"
 
@@ -148,10 +149,6 @@ namespace storm {
 
             qi::rule<Iterator, std::vector<storm::jani::Property>(), Skipper> start;
 
-            enum class ConstantDataType {
-                Bool, Integer, Rational
-            };
-
             qi::rule<Iterator, qi::unused_type(), qi::locals<ConstantDataType>, Skipper> constantDefinition;
             qi::rule<Iterator, std::string(), Skipper> identifier;
             qi::rule<Iterator, std::string(), Skipper> formulaName;