diff --git a/appshell/appshell_extensions_mac.mm b/appshell/appshell_extensions_mac.mm
index 373bdd0d6..d86051718 100644
--- a/appshell/appshell_extensions_mac.mm
+++ b/appshell/appshell_extensions_mac.mm
@@ -605,7 +605,17 @@ - (void) timeoutTimer:(NSTimer*)timer
 int32 ShowFolderInOSWindow(ExtensionString pathname)
 {
     NSString *filepath = [NSString stringWithUTF8String:pathname.c_str()];
-    [[NSWorkspace sharedWorkspace] activateFileViewerSelectingURLs:[NSArray arrayWithObject: [NSURL fileURLWithPath: filepath]]];
+    BOOL isDirectory;
+    
+    if (![[NSFileManager defaultManager] fileExistsAtPath:filepath isDirectory:&isDirectory]) {
+        return ERR_NOT_FOUND;
+    }
+
+    if (isDirectory) {
+        [[NSWorkspace sharedWorkspace] openFile:filepath];
+    } else {
+        [[NSWorkspace sharedWorkspace] activateFileViewerSelectingURLs:[NSArray arrayWithObject: [NSURL fileURLWithPath: filepath]]];
+    }
     return NO_ERROR;
 }
 
diff --git a/appshell/appshell_extensions_win.cpp b/appshell/appshell_extensions_win.cpp
index e3ecf7412..1a626ec5b 100644
--- a/appshell/appshell_extensions_win.cpp
+++ b/appshell/appshell_extensions_win.cpp
@@ -811,7 +811,26 @@ time_t FiletimeToTime(FILETIME const& ft) {
 }
 
 int32 ShowFolderInOSWindow(ExtensionString pathname) {
-    ShellExecute(NULL, L"open", pathname.c_str(), NULL, NULL, SW_SHOWDEFAULT);
+    ConvertToNativePath(pathname);
+    
+    DWORD dwAttr = GetFileAttributes(pathname.c_str());
+    if (dwAttr == INVALID_FILE_ATTRIBUTES) {
+        return ConvertWinErrorCode(GetLastError());
+    }
+    
+    if ((dwAttr & FILE_ATTRIBUTE_DIRECTORY) != 0) {
+        // Folder: open it directly, with nothing selected inside
+        ShellExecute(NULL, L"open", pathname.c_str(), NULL, NULL, SW_SHOWDEFAULT);
+        
+    } else {
+        // File: open its containing folder with this file selected
+        ITEMIDLIST *pidl = ILCreateFromPath(pathname.c_str());
+        if (pidl) {
+            SHOpenFolderAndSelectItems(pidl,0,0,0);
+            ILFree(pidl);
+        }
+    }
+    
     return NO_ERROR;
 }