diff --git a/Src/Base/AMReX_GpuTypes.H b/Src/Base/AMReX_GpuTypes.H
index ecb992983b..e01303656f 100644
--- a/Src/Base/AMReX_GpuTypes.H
+++ b/Src/Base/AMReX_GpuTypes.H
@@ -84,7 +84,7 @@ struct Handler
 
 struct Handler
 {
-    AMREX_GPU_HOST_DEVICE constexpr Handler (int n_active_threads = -1)
+    AMREX_GPU_HOST_DEVICE constexpr explicit Handler (int n_active_threads = -1)
         : numActiveThreads(n_active_threads) {}
 
     AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE