diff --git a/CHANGELOG b/CHANGELOG
index fd138e07b..5d2b429d1 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,7 +1,11 @@
 # Nmap Changelog ($Id$); -*-text-*-
 Nmap 4.20ALPHA3
 
-o Added back Win32 support thanks to a patch by kx (kxmail(a)gmail.com)
+o Added back Win32 support thanks to a patch by kx
+
+o Fix a problem which caused OS detection to be done in some cases
+  even if the user didn't request it.  Thanks to Diman Todorov for the
+  fix.
 
 Nmap 4.20ALPHA2
 
diff --git a/nmap.cc b/nmap.cc
index 7103950cc..9169f047a 100644
--- a/nmap.cc
+++ b/nmap.cc
@@ -1561,7 +1561,7 @@ int nmap_main(int argc, char *argv[]) {
       service_scan(Targets);
     }
 
-    if (o.osscan != OS_SCAN_SYS_1_ONLY)
+    if (o.osscan == OS_SCAN_DEFAULT || o.osscan == OS_SCAN_SYS_2_ONLY)
 	  os_scan_2(Targets);
 
     for(targetno = 0; targetno < Targets.size(); targetno++) {