diff --git a/compiler2/ttcn3/Ttcn2Json.cc b/compiler2/ttcn3/Ttcn2Json.cc
index 04360109f5dcffc8daf10387b09cae53a23416da..dc63c643faade855b075ea63b0e09a691c6de65d 100644
--- a/compiler2/ttcn3/Ttcn2Json.cc
+++ b/compiler2/ttcn3/Ttcn2Json.cc
@@ -129,9 +129,9 @@ JsonOmitCombination::~JsonOmitCombination()
   combinations.clear();
 }
 
-bool JsonOmitCombination::next(int current_value /* = 0 */)
+bool JsonOmitCombination::next(size_t current_value /* = 0 */)
 {
-  if ((size_t)current_value == combinations.size()) {
+  if (current_value == combinations.size()) {
     return false;
   }
   Common::Value* val = combinations.get_nth_key(current_value);
@@ -194,9 +194,9 @@ void JsonOmitCombination::parse_value(Common::Value* p_value)
   }
 }
 
-void JsonOmitCombination::reset_previous(int value_count)
+void JsonOmitCombination::reset_previous(size_t value_count)
 {
-  for (int i = 0; i < value_count; ++i) {
+  for (size_t i = 0; i < value_count; ++i) {
     Common::Value* val = combinations.get_nth_key(i);
     int* omitted_fields = combinations.get_nth_elem(i);
     for (size_t j = 0; j < val->get_nof_comps(); ++j) {
diff --git a/compiler2/ttcn3/Ttcn2Json.hh b/compiler2/ttcn3/Ttcn2Json.hh
index 51eb90adc73f2d18f52da839228d33e6597496bb..d7cb75434833480cfa26468e2a50af6c8b4d03ac 100644
--- a/compiler2/ttcn3/Ttcn2Json.hh
+++ b/compiler2/ttcn3/Ttcn2Json.hh
@@ -101,7 +101,7 @@ namespace Ttcn {
       * 
       * @return true, if the next combination was successfully generated, or
       * false, when called with the last combination */
-    bool next(int current_value = 0);
+    bool next(size_t current_value = 0);
     
     /** Returns the state of the specified record/set field in the current
       * combination. 
@@ -122,7 +122,7 @@ namespace Ttcn {
       * states to OMITTED_ABSENT.
       *
       * @param value_count specifies how many values to reset */
-    void reset_previous(int value_count);
+    void reset_previous(size_t value_count);
 
     /** Map containing the current combination.
       * Key: pointer to a record or set value in the AST (not owned)