diff --git a/fairmq/sdk/DDSTopology.cxx b/fairmq/sdk/DDSTopology.cxx
index 07389717..d4487174 100644
--- a/fairmq/sdk/DDSTopology.cxx
+++ b/fairmq/sdk/DDSTopology.cxx
@@ -59,7 +59,7 @@ auto DDSTopology::GetTopoFile() const -> Path
     return file;
 }
 
-auto DDSTopology::GetNumRequiredAgents() const -> int
+auto DDSTopology::GetNumRequiredAgents() const -> std::size_t
 {
     return fImpl->fTopo.getRequiredNofAgents();
 }
diff --git a/fairmq/sdk/DDSTopology.h b/fairmq/sdk/DDSTopology.h
index e4166d22..9a6a0597 100644
--- a/fairmq/sdk/DDSTopology.h
+++ b/fairmq/sdk/DDSTopology.h
@@ -50,7 +50,7 @@ class DDSTopology
     auto GetTopoFile() const -> Path;
 
     /// @brief Get number of required agents for this topology
-    auto GetNumRequiredAgents() const -> int;
+    auto GetNumRequiredAgents() const -> std::size_t;
 
     /// @brief Get list of tasks in this topology, optionally matching provided path
     auto GetTasks(const std::string& = "") const -> std::vector<DDSTask>;