--- a/Win32OperatingSystem.st	Mon Jul 17 17:50:51 2017 +0200
+++ b/Win32OperatingSystem.st	Tue Jul 18 10:19:14 2017 +0200
@@ -3632,12 +3632,17 @@
 
     cmdName := (aCommandString ? '') withoutSeparators.
 
-    (cmdName isEmpty or:[cmdName includesAny:'<>|']) ifFalse:[
+    (cmdName isEmpty or:[cmdName includesAny:'<>|&']) ifFalse:[
         "/ test whether the command is a plain executable;
         "/ if so, no shell is required
         |index file suffix|
 
-        index := cmdName indexOfSeparatorStartingAt:1.
+        cmdName first = $" ifTrue:[
+            index := cmdName indexOf:$" startingAt:2.
+        ] ifFalse:[
+            index := 1.
+        ].
+        index := cmdName indexOfSeparatorStartingAt:index.
         index ~~ 0 ifTrue:[
             cmdName := cmdName copyFrom:1 to:(index-1).
             args := cmdName copyFrom:(index+1).
@@ -3692,6 +3697,10 @@
      self commandAndArgsForOSCommand:'diff >nul:'
      self commandAndArgsForOSCommand:'diff /bla'
    "
+    "/ self commandAndArgsForOSCommand:'"C:\Program Files (x86)\Mozilla Firefox\firefox.exe" /bla'
+    "/ self commandAndArgsForOSCommand:'"C:\Program Files (x86)\Mozilla Firefox\firefox" /bla'
+    "/ self commandAndArgsForOSCommand:'"command with spaces" /bla'
+
 
     "Modified: / 20-01-1998 / 16:57:19 / md"
     "Modified: / 11-02-2007 / 20:51:08 / cg"