diff --git a/include/benchmark/reporter.h b/include/benchmark/reporter.h
index bb4ccdf..d23ab65 100644
--- a/include/benchmark/reporter.h
+++ b/include/benchmark/reporter.h
@@ -49,7 +49,7 @@
 
     std::string benchmark_name;
     std::string report_label;  // Empty if not set by benchmark.
-    size_t iterations;
+    int64_t iterations;
     double real_accumulated_time;
     double cpu_accumulated_time;
 
diff --git a/src/reporter.cc b/src/reporter.cc
index 5d6e722..4b47e3d 100644
--- a/src/reporter.cc
+++ b/src/reporter.cc
@@ -33,7 +33,7 @@
   Stat1_d items_per_second_stat;
   // All repetitions should be run with the same number of iterations so we
   // can take this information from the first benchmark.
-  std::size_t const run_iterations = reports.front().iterations;
+  int64_t const run_iterations = reports.front().iterations;
 
   // Populate the accumulators.
   for (Run const& run : reports) {