diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 57a50ed6970a1..5c28db96d936e 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -15255,8 +15255,13 @@ let
 
   mg = callPackage ../applications/editors/mg { };
 
-
-  # Attributes for backward compatibility.
+}
+  ### Aliases to attributes converted to the dashed-style.
+  // lib.mapAttrs (name: builtins.trace
+    ( "Warning: using a deprecated attribute '${name}'."
+    + " CamelCase and under_scores are replaced by dashed-names"
+    + " to match the nix-env names better."))
+{ # warnings since 2015-09
   adobeReader = adobe-reader;
   arduino_core = arduino-core;  # added 2015-02-04
   asciidocFull = asciidoc-full;  # added 2014-06-22
@@ -15265,8 +15270,6 @@ let
   lttngTools = lttng-tools;  # added 2014-07-31
   lttngUst = lttng-ust;  # added 2014-07-31
   jquery_ui = jquery-ui;  # added 2014-09-07
-  youtubeDL = youtube-dl;  # added 2014-10-26
-  youtube-dl = pythonPackages.youtube-dl; # added 2015-06-07
   rdiff_backup = rdiff-backup;  # added 2014-11-23
   htmlTidy = html-tidy;  # added 2014-12-06
   libtidy = html-tidy;  # added 2014-12-21
@@ -15274,8 +15277,17 @@ let
   sqliteInteractive = sqlite-interactive;  # added 2014-12-06
   nfsUtils = nfs-utils;  # added 2014-12-06
   buildbotSlave = buildbot-slave;  # added 2014-12-09
-  cool-old-term = cool-retro-term; # added 2015-01-31
   rssglx = rss-glx; #added 2015-03-25
+
+}
+  ### Other attribute aliases for backward compatibility.
+  // lib.mapAttrs
+      (name: builtins.trace "Warning: using a deprecated attribute '${name}'.")
+{ # warnings since 2015-09
+  youtubeDL = youtube-dl;  # added 2014-10-26
+  youtube-dl = pythonPackages.youtube-dl; # added 2015-06-07
+  cool-old-term = cool-retro-term; # added 2015-01-31
+
   haskell-ng = haskell;                 # 2015-04-19
   haskellngPackages = haskellPackages;  # 2015-04-19
   inherit (haskell.compiler) jhc uhc;   # 2015-05-15