diff --git a/emper/lib/sync/SpuriousFutexSemaphore.hpp b/emper/lib/sync/SpuriousFutexSemaphore.hpp
index ae202f592518692dac487cfa72d7c6672026df64..fa40a3bbacecaabb9ac410d0291966be6090667e 100644
--- a/emper/lib/sync/SpuriousFutexSemaphore.hpp
+++ b/emper/lib/sync/SpuriousFutexSemaphore.hpp
@@ -20,7 +20,7 @@ namespace emper::lib::sync {
 // by only using a single atomic operation and a possible system call per method.
 class SpuriousFutexSemaphore {
  public:
-	using CounterType = long;
+	using CounterType = int32_t;
 
  private:
 	// >= 0 means no waiters