diff --git a/doc/manual/nix-hash.xml b/doc/manual/nix-hash.xml
index 007fc54100..af4e361ff8 100644
--- a/doc/manual/nix-hash.xml
+++ b/doc/manual/nix-hash.xml
@@ -91,8 +91,9 @@ cryptographic hash as <literal>nix-store --dump
 
   <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
 
-    <listitem><para>Specify a cryptographic hash, which can be one of
-    <literal>md5</literal>, <literal>sha1</literal>, and
+    <listitem><para>Use the specified cryptographic hash algorithm,
+    which can be one of <literal>md5</literal>,
+    <literal>sha1</literal>, and
     <literal>sha256</literal>.</para></listitem>
 
   </varlistentry>
diff --git a/doc/manual/nix-prefetch-url.xml b/doc/manual/nix-prefetch-url.xml
index 0d953e9467..c416e675b0 100644
--- a/doc/manual/nix-prefetch-url.xml
+++ b/doc/manual/nix-prefetch-url.xml
@@ -18,6 +18,7 @@
 <refsynopsisdiv>
   <cmdsynopsis>
     <command>nix-prefetch-url</command>
+    <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
     <arg choice='plain'><replaceable>url</replaceable></arg>
     <arg><replaceable>hash</replaceable></arg>
   </cmdsynopsis>
@@ -45,11 +46,6 @@ download it again when you build your Nix expression.  Since
 as <command>nix-prefetch-url</command>, the redundant download can be
 avoided.</para>
 
-<para>The environment variable <envar>NIX_HASH_ALGO</envar> specifies
-which hash algorithm to use.  It can be either <literal>md5</literal>,
-<literal>sha1</literal>, or <literal>sha256</literal>.  The default is
-<literal>sha256</literal>.</para>
-
 <para>If <replaceable>hash</replaceable> is specified, then a download
 is not performed if the Nix store already contains a file with the
 same hash and base name.  Otherwise, the file is downloaded, and an
@@ -63,6 +59,24 @@ of the downloaded file in the Nix store is also printed.</para>
 </refsection>
 
 
+<refsection><title>Options</title>
+
+<variablelist>
+  
+  <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
+
+    <listitem><para>Use the specified cryptographic hash algorithm,
+    which can be one of <literal>md5</literal>,
+    <literal>sha1</literal>, and
+    <literal>sha256</literal>.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
 <refsection><title>Examples</title>
 
 <screen>
diff --git a/scripts/nix-prefetch-url.in b/scripts/nix-prefetch-url.in
index 64102e8ae8..bcd9197bcf 100755
--- a/scripts/nix-prefetch-url.in
+++ b/scripts/nix-prefetch-url.in
@@ -8,11 +8,28 @@ use Nix::Store;
 use Nix::Config;
 use Nix::Utils;
 
-my $url = shift;
-my $expHash = shift;
-my $hashType = $ENV{'NIX_HASH_ALGO'} || "sha256";
+my $hashType = $ENV{'NIX_HASH_ALGO'} || "sha256"; # obsolete
 my $cacheDir = $ENV{'NIX_DOWNLOAD_CACHE'};
 
+my @args;
+my $arg;
+while ($arg = shift) {
+    if ($arg eq "--help") {
+        exec "man nix-prefetch-url" or die;
+    } elsif ($arg eq "--type") {
+        $hashType = shift;
+        die "$0: `$arg' requires an argument\n" unless defined $hashType;
+    } elsif (substr($arg, 0, 1) eq "-") {
+        die "$0: unknown flag `$arg'\n";
+    } else {
+        push @args, $arg;
+    }
+}
+
+my $url = $args[0];
+my $expHash = $args[1];
+
+
 if (!defined $url || $url eq "") {
     print STDERR <<EOF
 Usage: nix-prefetch-url URL [EXPECTED-HASH]