diff --git a/CHANGES b/CHANGES
index a2cd9b4d02..8e363749f7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+2196.	[port]		win32: yield processor while waiting for once to
+			to complete. [RT# 16958]
+
 2195.	[func]		dnssec-keygen now defaults to nametype "ZONE"
 			when generating DNSKEYs. [RT #16954]
 
diff --git a/lib/isc/win32/once.c b/lib/isc/win32/once.c
index b38e38c415..76dd82dfe4 100644
--- a/lib/isc/win32/once.c
+++ b/lib/isc/win32/once.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: once.c,v 1.10 2004/03/05 05:11:58 marka Exp $ */
+/* $Id: once.c,v 1.11 2007/06/18 01:16:46 marka Exp $ */
 
 /* Principal Authors: DCL */
 
@@ -41,8 +41,11 @@ isc_once_do(isc_once_t *controller, void(*function)(void)) {
 		} else {
 			while (controller->status == ISC_ONCE_INIT_NEEDED) {
 				/*
-				 * Spin wait.
+				 * Sleep(0) indicates that this thread 
+				 * should be suspended to allow other 
+				 * waiting threads to execute.
 				 */
+				Sleep(0);
 			}
 		}
 	}