diff --git a/scripts/nix-generate-regscript b/scripts/nix-generate-regscript
new file mode 100755
index 0000000000..bf370f8d78
--- /dev/null
+++ b/scripts/nix-generate-regscript
@@ -0,0 +1,20 @@
+#! /usr/bin/perl -w
+
+my $dir = shift @ARGV;
+$dir || die "missing directory";
+my $url = shift @ARGV;
+$url || die "missing base url";
+
+chdir $dir || die "cannot chdir to $dir";
+
+foreach my $prebuilt (glob("*.tar.bz2")) {
+
+    $prebuilt =~ /-([a-z0-9]+)-([a-z0-9]+).tar.bz2$/
+	|| die "invalid file name: $prebuilt";
+
+    my $pkgHash = $1;
+    my $prebuiltHash = $2;
+
+    print "regprebuilt $pkgHash $prebuiltHash\n";
+    print "regurl $prebuiltHash $url/$prebuilt\n";
+}
diff --git a/src/fix.cc b/src/fix.cc
index cb19909284..bf335bc365 100644
--- a/src/fix.cc
+++ b/src/fix.cc
@@ -1,6 +1,9 @@
 #include <iostream>
 #include <map>
 
+#include <sys/types.h>
+#include <sys/wait.h>
+
 extern "C" {
 #include <aterm2.h>
 }
@@ -23,13 +26,31 @@ void registerFile(string filename)
 }
 
 
+/* Return the directory part of the given path, i.e., everything
+   before the final `/'. */
+string dirOf(string s)
+{
+    unsigned int pos = s.rfind('/');
+    if (pos == string::npos) throw Error("invalid file name");
+    return string(s, 0, pos);
+}
+
+
+/* Return the base name of the given path, i.e., everything following
+   the final `/'. */
+string baseNameOf(string s)
+{
+    unsigned int pos = s.rfind('/');
+    if (pos == string::npos) throw Error("invalid file name");
+    return string(s, pos + 1);
+}
+
+
 /* Download object referenced by the given URL into the sources
    directory.  Return the file name it was downloaded to. */
 string fetchURL(string url)
 {
-    unsigned int pos = url.rfind('/');
-    if (pos == string::npos) throw Error("invalid url");
-    string filename(url, pos + 1);
+    string filename = baseNameOf(url);
     string fullname = nixSourcesDir + "/" + filename;
     /* !!! quoting */
     string shellCmd =
@@ -41,16 +62,6 @@ string fetchURL(string url)
 }
 
 
-/* Return the directory part of the given path, i.e., everything
-   before the final `/'. */
-string dirOf(string s)
-{
-    unsigned int pos = s.rfind('/');
-    if (pos == string::npos) throw Error("invalid file name");
-    return string(s, 0, pos);
-}
-
-
 /* Term evaluation functions. */
 
 string evaluateStr(ATerm e)
@@ -88,12 +99,13 @@ string evaluateFile(ATerm e, string dir)
         int res = system(cmd.c_str());
         if (WEXITSTATUS(res) != 0)
             throw Error("cannot copy " + filename);
+        registerFile(nixSourcesDir + "/" + baseNameOf(filename));
         return hashFile(filename);
     } else throw Error("invalid hash expression");
 }
 
 
-ATerm evaluatePkg(ATerm e, DescriptorMap & done)
+string evaluatePkg(ATerm e, DescriptorMap & done)
 {
     char * s;
     if (ATmatch(e, "<str>", &s)) {
@@ -113,7 +125,7 @@ ATerm evaluate(ATerm e, string dir, DescriptorMap & done)
     else if (ATmatch(e, "File(<term>)", &t))
         return ATmake("File(<str>)", evaluateFile(t, dir).c_str());
     else if (ATmatch(e, "Pkg(<term>)", &t))
-        return ATmake("Pkg(<term>)", evaluatePkg(t, done));
+        return ATmake("Pkg(<str>)", evaluatePkg(t, done).c_str());
     else throw Error("invalid expression type");
 }
 
diff --git a/src/nix-regprebuilts b/src/nix-regprebuilts
deleted file mode 100755
index 6c9c981eee..0000000000
--- a/src/nix-regprebuilts
+++ /dev/null
@@ -1,17 +0,0 @@
-#! /usr/bin/perl -w
-
-my $dir = $ARGV[0];
-
-foreach my $prebuilt (glob("$dir/*.tar.bz2")) {
-
-    $prebuilt =~ /-([a-z0-9]+)-([a-z0-9]+).tar.bz2$/
-	|| die "invalid file name: $prebuilt";
-
-    my $pkgHash = $1;
-    my $prebuiltHash = $2;
-
-    print "$pkgHash -> $prebuiltHash\n";
-
-    system "nix regprebuilt $pkgHash $prebuiltHash";
-    system "nix regfile $prebuilt";
-}
diff --git a/src/nix.cc b/src/nix.cc
index 9e42917a49..9364baf6ca 100644
--- a/src/nix.cc
+++ b/src/nix.cc
@@ -6,11 +6,12 @@
 #include <map>
 #include <cstdio>
 
+#include <errno.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#include <db4/db_cxx.h>
+#include <db_cxx.h>
 
 extern "C" {
 #include <aterm1.h>
@@ -48,9 +49,7 @@ public:
 
 auto_ptr<Db2> openDB(const string & dbname, bool readonly)
 {
-    auto_ptr<Db2> db;
-
-    db = auto_ptr<Db2>(new Db2(0, 0));
+    auto_ptr<Db2> db(new Db2(0, 0));
 
     db->open((nixHomeDir + "/var/nix/pkginfo.db").c_str(), dbname.c_str(),
         DB_HASH, readonly ? DB_RDONLY : DB_CREATE, 0666);