diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0e81f7b72..66173cdaf 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -401,17 +401,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
         HashType ht = parseHashType(outputHashAlgo);
         if (ht == htUnknown)
             throw EvalError(format("unknown hash algorithm `%1%'") % outputHashAlgo);
-        Hash h(ht);
-        if (outputHash.size() == h.hashSize * 2)
-            /* hexadecimal representation */
-            h = parseHash(ht, outputHash);
-        else if (outputHash.size() == hashLength32(h))
-            /* base-32 representation */
-            h = parseHash32(ht, outputHash);
-        else
-            throw Error(format("hash `%1%' has wrong length for hash type `%2%'")
-                % outputHash % outputHashAlgo);
-        string s = outputHash;
+        Hash h = parseHash16or32(ht, outputHash);
         outputHash = printHash(h);
         if (outputHashRecursive) outputHashAlgo = "r:" + outputHashAlgo;
         
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index b9e784699..533423441 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -204,6 +204,22 @@ Hash parseHash32(HashType ht, const string & s)
 }
 
 
+Hash parseHash16or32(HashType ht, const string & s)
+{
+    Hash hash(ht);
+    if (s.size() == hash.hashSize * 2)
+        /* hexadecimal representation */
+        hash = parseHash(ht, s);
+    else if (s.size() == hashLength32(hash))
+        /* base-32 representation */
+        hash = parseHash32(ht, s);
+    else
+        throw Error(format("hash `%1%' has wrong length for hash type `%2%'")
+            % s % printHashType(ht));
+    return hash;
+}
+
+
 bool isHash(const string & s)
 {
     if (s.length() != 32) return false;
diff --git a/src/libutil/hash.hh b/src/libutil/hash.hh
index 13740954d..cbdcf4c8d 100644
--- a/src/libutil/hash.hh
+++ b/src/libutil/hash.hh
@@ -58,6 +58,9 @@ string printHash32(const Hash & hash);
 /* Parse a base-32 representation of a hash code. */
 Hash parseHash32(HashType ht, const string & s);
 
+/* Parse a base-16 or base-32 representation of a hash code. */
+Hash parseHash16or32(HashType ht, const string & s);
+
 /* Verify that the given string is a valid hash code. */
 bool isHash(const string & s);
 
diff --git a/src/nix-hash/nix-hash.cc b/src/nix-hash/nix-hash.cc
index 4867234bf..5b35ccd9d 100644
--- a/src/nix-hash/nix-hash.cc
+++ b/src/nix-hash/nix-hash.cc
@@ -43,7 +43,7 @@ void run(Strings args)
     }
 
     if (op == opHash) {
-        for (Strings::iterator i = ss.begin(); i != ss.end(); ++i) {
+        foreach (Strings::iterator, i, ss) {
             Hash h = flat ? hashFile(ht, *i) : hashPath(ht, *i).first;
             if (truncate && h.hashSize > 20) h = compressHash(h, 20);
             std::cout << format("%1%\n") %
@@ -52,8 +52,8 @@ void run(Strings args)
     }
 
     else {
-        for (Strings::iterator i = ss.begin(); i != ss.end(); ++i) {
-            Hash h = op == opTo16 ? parseHash32(ht, *i) : parseHash(ht, *i);
+        foreach (Strings::iterator, i, ss) {
+            Hash h = parseHash16or32(ht, *i);
             std::cout << format("%1%\n") %
                 (op == opTo16 ? printHash(h) : printHash32(h));
         }
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 84d3da032..740033b45 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -133,14 +133,6 @@ static void opAddFixed(Strings opFlags, Strings opArgs)
 }
 
 
-static Hash parseHash16or32(HashType ht, const string & s)
-{
-    return s.size() == Hash(ht).hashSize * 2
-        ? parseHash(ht, s)
-        : parseHash32(ht, s);
-}
-
-
 /* Hack to support caching in `nix-prefetch-url'. */
 static void opPrintFixedPath(Strings opFlags, Strings opArgs)
 {