diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml
index 0a69f43b1fc..6fbd7c269c4 100644
--- a/doc/manual/release-notes.xml
+++ b/doc/manual/release-notes.xml
@@ -14,6 +14,11 @@
 
 <itemizedlist>
 
+  <listitem>
+    <para>Dashes are now valid as part of identifiers and attribute
+    names.</para>
+  </listitem>
+
   <listitem>
     <para>Nix no longer sets the immutable bit on files in the Nix
     store.  Instead, the recommended way to guard the Nix store
diff --git a/misc/emacs/nix-mode.el b/misc/emacs/nix-mode.el
index 121a9172b63..986edcf6e32 100644
--- a/misc/emacs/nix-mode.el
+++ b/misc/emacs/nix-mode.el
@@ -78,7 +78,7 @@ The hook `nix-mode-hook' is run when Nix mode is started.
     ("\\<isNull\\>" . font-lock-builtin-face)
     ("[a-zA-Z][a-zA-Z0-9\\+-\\.]*:[a-zA-Z0-9%/\\?:@&=\\+\\$,_\\.!~\\*'-]+"
      . font-lock-constant-face)
-    ("\\<\\([a-zA-Z_][a-zA-Z0-9_'\.]*\\)[ \t]*="
+    ("\\<\\([a-zA-Z_][a-zA-Z0-9_'\-\.]*\\)[ \t]*="
      (1 font-lock-variable-name-face nil nil))
     ("<[a-zA-Z0-9._\\+-]+\\(/[a-zA-Z0-9._\\+-]+\\)*>"
      . font-lock-constant-face)
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index d46b66d9ff7..b61d5ea7713 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -78,7 +78,7 @@ static Expr * unescapeStr(SymbolTable & symbols, const char * s)
 %}
 
 
-ID          [a-zA-Z\_][a-zA-Z0-9\_\']*
+ID          [a-zA-Z\_][a-zA-Z0-9\_\'\-]*
 INT         [0-9]+
 PATH        [a-zA-Z0-9\.\_\-\+]*(\/[a-zA-Z0-9\.\_\-\+]+)+
 SPATH       \<[a-zA-Z0-9\.\_\-\+]+(\/[a-zA-Z0-9\.\_\-\+]+)*\>
diff --git a/tests/lang/eval-okay-attrs5.nix b/tests/lang/eval-okay-attrs5.nix
index e77ee7a1c22..0a98b8fdffa 100644
--- a/tests/lang/eval-okay-attrs5.nix
+++ b/tests/lang/eval-okay-attrs5.nix
@@ -4,7 +4,7 @@ let
 
   as = { x.y.z = 123; a.b.c = 456; };
 
-  bs = { foo.bar = "foo"; };
+  bs = { f-o-o.bar = "foo"; };
 
   or = x: y: x || y;
   
@@ -13,7 +13,7 @@ in
     as.foo or "foo"
     as.x.y.bla or as.a.b.c
     as.a.b.c or as.x.y.z
-    as.x.y.bla or bs.foo.bar or "xyzzy"
+    as.x.y.bla or bs.f-o-o.bar or "xyzzy"
     as.x.y.bla or bs.bar.foo or "xyzzy"
     123.bla or null.foo or "xyzzy"
     # Backwards compatibility test.