4 files changed, 24 insertions, 5 deletions
diff --git a/src/fix-ng/eval.cc b/src/fix-ng/eval.cc
index 38a1d81fcfe4..726bc5daeb44 100644
--- a/src/fix-ng/eval.cc
+++ b/src/fix-ng/eval.cc
@@ -109,8 +109,8 @@ Path evalPath(EvalState & state, Expr e)
 bool evalBool(EvalState & state, Expr e)
 {
     e = evalExpr(state, e);
-    if (ATmatch(e, "True")) return true;
-    else if (ATmatch(e, "False")) return false;
+    if (ATmatch(e, "Bool(True)")) return true;
+    else if (ATmatch(e, "Bool(False)")) return false;
     else throw badTerm("expecting a boolean", e);
 }
 
@@ -124,6 +124,7 @@ Expr evalExpr2(EvalState & state, Expr e)
     if (ATmatch(e, "Str(<str>)", &s1) ||
         ATmatch(e, "Path(<str>)", &s1) ||
         ATmatch(e, "Uri(<str>)", &s1) ||
+        ATmatch(e, "Bool(<term>)", &e1) ||
         ATmatch(e, "Function([<list>], <term>)", &e1, &e2) ||
         ATmatch(e, "Attrs([<list>])", &e1) ||
         ATmatch(e, "List([<list>])", &e1))
@@ -188,7 +189,7 @@ Expr evalExpr2(EvalState & state, Expr e)
     if (ATmatch(e, "OpEq(<term>, <term>)", &e1, &e2)) {
         string s1 = evalString(state, e1);
         string s2 = evalString(state, e2);
-        return s1 == s2 ? ATmake("True") : ATmake("False");
+        return s1 == s2 ? ATmake("Bool(True)") : ATmake("Bool(False)");
     }
 
     /* Barf. */
diff --git a/src/fix-ng/fix.sdf b/src/fix-ng/fix.sdf
index 251a63f0c5fb..8effe6d21d98 100644
--- a/src/fix-ng/fix.sdf
+++ b/src/fix-ng/fix.sdf
@@ -68,6 +68,9 @@ exports
     Expr "==" Expr
     -> Expr {cons("OpEq")}
 
+    Bool
+    -> Expr {cons("Bool")}
+
   context-free priorities
 
     Expr "." Id -> Expr
@@ -84,10 +87,19 @@ exports
   lexical syntax
     [a-zA-Z\_][a-zA-Z0-9\_\']* -> Id
     "rec" -> Id {reject}
+    "true" -> Id {reject}
+    "false" -> Id {reject}
+
     [0-9]+ -> Int
+
     "\"" ~[\n\"]* "\"" -> Str
+
     PathComp ("/" PathComp)+ -> Path
     [a-zA-Z0-9\.\_\-]+ -> PathComp
+
+    "true" -> Bool
+    "false" -> Bool
+
   lexical restrictions
     Id -/- [a-zA-Z0-9\_\']
     Int -/- [0-9]
diff --git a/src/fix-ng/parser.cc b/src/fix-ng/parser.cc
index d310397c2d63..7dff0363dbc5 100644
--- a/src/fix-ng/parser.cc
+++ b/src/fix-ng/parser.cc
@@ -50,6 +50,12 @@ struct Cleanup : TermFun
             return ATmake("Int(<int>)", n);
         }
 
+        if (ATmatch(e, "Bool(\"true\")", &s))
+            return ATmake("Bool(True)");
+        
+        if (ATmatch(e, "Bool(\"false\")", &s))
+            return ATmake("Bool(False)");
+
         return e;
     }
 };
diff --git a/src/fix-ng/primops.cc b/src/fix-ng/primops.cc
index 7d060124b74c..f887d265f326 100644
--- a/src/fix-ng/primops.cc
+++ b/src/fix-ng/primops.cc
@@ -84,8 +84,8 @@ static string processBinding(EvalState & state, Expr e, NixExpr & ne)
 
     if (ATmatch(e, "Str(<str>)", &s)) return s;
     if (ATmatch(e, "Uri(<str>)", &s)) return s;
-    if (ATmatch(e, "True")) return "1";
-    if (ATmatch(e, "False")) return "";
+    if (ATmatch(e, "Bool(True)")) return "1";
+    if (ATmatch(e, "Bool(False)")) return "";
 
     if (ATmatch(e, "Attrs([<list>])", &es)) {
         Expr a = queryAttr(e, "type");