diff --git a/src/signalhandler_unittest.cc b/src/signalhandler_unittest.cc
index 05a5b96..5493e52 100644
--- a/src/signalhandler_unittest.cc
+++ b/src/signalhandler_unittest.cc
@@ -44,7 +44,12 @@
 using namespace GOOGLE_NAMESPACE;
 
 void* DieInThread(void*) {
-  fprintf(stderr, "0x%lx is dying\n", pthread_self());
+  // We assume pthread_t is an integral number or a pointer, rather
+  // than a complex struct.  In some environments, pthread_self()
+  // returns an uint64 but in some other environments pthread_self()
+  // returns a pointer.  Hence we use C-style cast here, rather than
+  // reinterpret/static_cast, to support both types of environments.
+  fprintf(stderr, "0x%lx is dying\n", (long)pthread_self());
   // Use volatile to prevent from these to be optimized away.
   volatile int a = 0;
   volatile int b = 1 / a;