diff --git a/src/hdf5_array.hpp b/src/hdf5_array.hpp
index 4cab937..9587189 100644
--- a/src/hdf5_array.hpp
+++ b/src/hdf5_array.hpp
@@ -144,8 +144,8 @@ namespace CosmoTool {
                         bool useBases = false)
   {
       std::vector<hsize_t> memdims(data.shape(), data.shape() + data.num_dimensions());
-      H5::DataSpace dataspace(dimensions.size(), dimensions.data());
-      H5::DataSpace memspace(memdims.size(), memdims.data());
+      H5::DataSpace dataspace(int(dimensions.size()), dimensions.data());
+      H5::DataSpace memspace(int(memdims.size()), memdims.data());
 
       if (useBases) {
         std::vector<hsize_t> offsets(data.index_bases(), data.index_bases() + data.num_dimensions());
@@ -398,7 +398,7 @@ namespace CosmoTool {
             hdf5_weak_check_array(data, dimensions);
 
             std::vector<hsize_t> memdims(data.shape(), data.shape() + data.num_dimensions());
-            H5::DataSpace memspace(memdims.size(), memdims.data());
+            H5::DataSpace memspace(int(memdims.size()), memdims.data());
             
             std::vector<hsize_t> offsets(data.index_bases(), data.index_bases() + data.num_dimensions());            
             dataspace.selectHyperslab(H5S_SELECT_SET, memdims.data(), offsets.data());