diff --git a/lib/opencl_boinc.cpp b/lib/opencl_boinc.cpp
index 227b2944df..12a1aaa5b0 100644
--- a/lib/opencl_boinc.cpp
+++ b/lib/opencl_boinc.cpp
@@ -66,7 +66,7 @@ void OPENCL_DEVICE_PROP::write_xml(MIOFILE& f, const char* tag, bool temp_file)
         tag,
         name,
         vendor,
-        (long)vendor_id,
+        (unsigned long)vendor_id,
         available ? 1 : 0,
         half_fp_config,
         single_fp_config,
@@ -76,8 +76,8 @@ void OPENCL_DEVICE_PROP::write_xml(MIOFILE& f, const char* tag, bool temp_file)
         extensions,
         global_mem_size,
         local_mem_size,
-        (long)max_clock_frequency,
-        (long)max_compute_units,
+        (unsigned long)max_clock_frequency,
+        (unsigned long)max_compute_units,
         opencl_platform_version,
         opencl_device_version,
         opencl_driver_version