diff --git a/unittests/map.hpp b/unittests/map.hpp
index 5a91509b..e44a5f47 100644
--- a/unittests/map.hpp
+++ b/unittests/map.hpp
@@ -62,7 +62,7 @@ void test_map()
 
     std::map<int8_t, StructExternalSplit> o_esplmap;
     for(int j=0; j<100; ++j)
-      o_esplmap.insert({random_value<char>(gen),  { random_value<int>(gen), random_value<int>(gen) }});
+      o_esplmap.insert({random_value<int8_t>(gen),  { random_value<int>(gen), random_value<int>(gen) }});
 
     std::ostringstream os;
     {
diff --git a/unittests/multimap.hpp b/unittests/multimap.hpp
index 0e74b1b8..cc0f50bf 100644
--- a/unittests/multimap.hpp
+++ b/unittests/multimap.hpp
@@ -71,7 +71,7 @@ void test_multimap()
     std::multimap<int8_t, StructExternalSplit> o_esplmultimap;
     for(int j=0; j<100; ++j)
     {
-      auto key = random_value<char>(gen);
+      auto key = random_value<int8_t>(gen);
       o_esplmultimap.insert({key,  { random_value<int>(gen), random_value<int>(gen) }});
       o_esplmultimap.insert({key,  { random_value<int>(gen), random_value<int>(gen) }});
     }
diff --git a/unittests/unordered_map.hpp b/unittests/unordered_map.hpp
index cc50e788..aa307b37 100644
--- a/unittests/unordered_map.hpp
+++ b/unittests/unordered_map.hpp
@@ -54,7 +54,7 @@ void test_unordered_map()
 
     std::unordered_map<int8_t, StructExternalSplit> o_esplunordered_map;
     for(int j=0; j<100; ++j)
-      o_esplunordered_map.insert({random_value<char>(gen),  { random_value<int>(gen), random_value<int>(gen) }});
+      o_esplunordered_map.insert({random_value<int8_t>(gen),  { random_value<int>(gen), random_value<int>(gen) }});
 
     std::ostringstream os;
     {
diff --git a/unittests/unordered_multimap.hpp b/unittests/unordered_multimap.hpp
index d5d76bc4..5b3048e8 100644
--- a/unittests/unordered_multimap.hpp
+++ b/unittests/unordered_multimap.hpp
@@ -71,7 +71,7 @@ void test_unordered_multimap()
     std::unordered_multimap<int8_t, StructExternalSplit> o_esplunordered_multimap;
     for(int j=0; j<100; ++j)
     {
-      auto key = random_value<char>(gen);
+      auto key = random_value<int8_t>(gen);
       o_esplunordered_multimap.insert({key,  { random_value<int>(gen), random_value<int>(gen) }});
       o_esplunordered_multimap.insert({key,  { random_value<int>(gen), random_value<int>(gen) }});
     }