diff --git a/src/cdf.c b/src/cdf.c
index cde2c37a7fdb704edbdd61eab65346b6e0e9a63e..6fb0a85528b16425f3164919830fe574ccf99373 100644
--- a/src/cdf.c
+++ b/src/cdf.c
@@ -41,8 +41,11 @@ const char *hdfLibraryVersion(void)
 
   H5get_libversion(&majnum, &minnum, &relnum);
 
+#if  defined(HAVE_NC4HDF5_THREADSAFE)
+  sprintf(hdf_libvers, "%u.%u.%u threadsafe", majnum, minnum, relnum);
+#else
   sprintf(hdf_libvers, "%u.%u.%u", majnum, minnum, relnum);
-
+#endif
   return hdf_libvers;
 #else
   return "library undefined";