diff --git a/CHANGELOG b/CHANGELOG
index 90a2f7d5a..937725c12 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,10 @@
 #Nmap Changelog ($Id$); -*-text-*-
 
+o [GH#1192][Windows] Periodically reset the system idle timer to keep the
+  system from going to sleep while scans are in process. This only affects port
+  scans and OS detection scans, since NSE and version scan do not rely on
+  timing data to adjust speed.
+
 o [GH#1023] Handle Internationalized Domain Names (IDN) like Яндекс.рф on
   platforms where getaddrinfo supports the AI_IDN flag. [Daniel Miller]
 
diff --git a/FPEngine.cc b/FPEngine.cc
index ca0622360..9b04984a1 100644
--- a/FPEngine.cc
+++ b/FPEngine.cc
@@ -1173,6 +1173,10 @@ int FPEngine6::os_scan(std::vector<Target *> &Targets) {
         (int) curr_hosts.size(), (int) left_hosts.size(), (int) done_hosts.size());
     }
 
+#ifdef WIN32
+    // Reset system idle timer to avoid going to sleep
+    SetThreadExecutionState(ES_SYSTEM_REQUIRED);
+#endif
     /* Go through the list of hosts and ask them to schedule their probes */
     for (unsigned int i = 0; i < curr_hosts.size(); i++) {
 
diff --git a/osscan2.cc b/osscan2.cc
index 8ff520eea..f9c9f87ac 100644
--- a/osscan2.cc
+++ b/osscan2.cc
@@ -3663,6 +3663,10 @@ int OSScan::os_scan_ipv4(std::vector<Target *> &Targets) {
   /* Initialize the pcap session handler in HOS */
   begin_sniffer(&HOS, Targets);
   while (OSI.numIncompleteHosts() != 0) {
+#ifdef WIN32
+    // Reset system idle timer to avoid going to sleep
+    SetThreadExecutionState(ES_SYSTEM_REQUIRED);
+#endif
     if (itry > 0)
       sleep(1);
     if (itry == 3)
diff --git a/scan_engine.cc b/scan_engine.cc
index a15cee0ed..c8b4c516f 100644
--- a/scan_engine.cc
+++ b/scan_engine.cc
@@ -2777,6 +2777,10 @@ void ultra_scan(std::vector<Target *> &Targets, const struct scan_lists *ports,
   /* Otherwise, no sniffer needed! */
 
   while (!USI.incompleteHostsEmpty()) {
+#ifdef WIN32
+    // Reset system idle timer to avoid going to sleep
+    SetThreadExecutionState(ES_SYSTEM_REQUIRED);
+#endif
     doAnyPings(&USI);
     doAnyOutstandingRetransmits(&USI); // Retransmits from probes_outstanding
     /* Retransmits from retry_stack -- goes after OutstandingRetransmits for