diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 262e3bec54..4cd180fd60 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -488,9 +488,9 @@ static string relativise(Path pivot, Path p)
     /* Otherwise, `p' is in a parent of `pivot'.  Find up till which
        path component `p' and `pivot' match, and add an appropriate
        number of `..' components. */
-    unsigned int i = 1;
+    string::size_type i = 1;
     while (1) {
-        unsigned int j = pivot.find('/', i);
+        string::size_type j = pivot.find('/', i);
         if (j == string::npos) break;
         j++;
         if (pivot.substr(0, j) != p.substr(0, j)) break;
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index c2bc5bdb1b..dc0b078e52 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -212,7 +212,7 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
         string contents = readFile(*fd);
 
         /* Extract the roots. */
-        unsigned int pos = 0, end;
+        string::size_type pos = 0, end;
 
         while ((end = contents.find((char) 0, pos)) != string::npos) {
             Path root(contents, pos, end - pos);
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index fc338892f2..194e1165fa 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -46,7 +46,7 @@ static void readSettings()
             line += contents[pos++];
         pos++;
 
-        unsigned int hash = line.find('#');
+        string::size_type hash = line.find('#');
         if (hash != string::npos)
             line = string(line, 0, hash);
 
diff --git a/src/libstore/references.cc b/src/libstore/references.cc
index 4e4bb7ad1e..d67e5b9dcc 100644
--- a/src/libstore/references.cc
+++ b/src/libstore/references.cc
@@ -99,7 +99,7 @@ PathSet scanForReferences(const string & path, const PathSet & paths)
        have the form `HASH-bla'). */
     for (PathSet::const_iterator i = paths.begin(); i != paths.end(); i++) {
         string baseName = baseNameOf(*i);
-        unsigned int pos = baseName.find('-');
+        string::size_type pos = baseName.find('-');
         if (pos == string::npos)
             throw Error(format("bad reference `%1%'") % *i);
         string s = string(baseName, 0, pos);
diff --git a/src/libstore/store.cc b/src/libstore/store.cc
index 556ba8e621..4bf62570e6 100644
--- a/src/libstore/store.cc
+++ b/src/libstore/store.cc
@@ -243,7 +243,7 @@ Path toStorePath(const Path & path)
 {
     if (!isInStore(path))
         throw Error(format("path `%1%' is not in the Nix store") % path);
-    unsigned int slash = path.find('/', nixStore.size() + 1);
+    Path::size_type slash = path.find('/', nixStore.size() + 1);
     if (slash == Path::npos)
         return path;
     else
@@ -563,7 +563,7 @@ static Hash queryHash(const Transaction & txn, const Path & storePath)
 {
     string s;
     nixDB.queryString(txn, dbValidPaths, storePath, s);
-    unsigned int colon = s.find(':');
+    string::size_type colon = s.find(':');
     if (colon == string::npos)
         throw Error(format("corrupt hash `%1%' in valid-path entry for `%2%'")
             % s % storePath);
diff --git a/src/libutil/aterm-map.cc b/src/libutil/aterm-map.cc
index f400464378..33388e148a 100644
--- a/src/libutil/aterm-map.cc
+++ b/src/libutil/aterm-map.cc
@@ -111,34 +111,35 @@ void ATermMap::copy(KeyValue * elements, unsigned int capacity)
 }
 
 
+/* !!! use a bigger shift for 64-bit platforms? */
 static const unsigned int shift = 16;
-static const unsigned int knuth = (unsigned int) (0.6180339887 * (1 << shift));
+static const unsigned long knuth = (unsigned long) (0.6180339887 * (1 << shift));
 
 
-unsigned int ATermMap::hash1(ATerm key) const
+unsigned long ATermMap::hash1(ATerm key) const
 {
     /* Don't care about the least significant bits of the ATerm
        pointer since they're always 0. */
-    unsigned int key2 = ((unsigned int) key) >> 2;
+    unsigned long key2 = ((unsigned long) key) >> 2;
 
     /* Approximately equal to:
     double d = key2 * 0.6180339887;
     unsigned int h = (int) (capacity * (d - floor(d)));
     */
  
-    unsigned int h = (capacity * ((key2 * knuth) & ((1 << shift) - 1))) >> shift;
+    unsigned long h = (capacity * ((key2 * knuth) & ((1 << shift) - 1))) >> shift;
 
     return h;
 }
 
 
-unsigned int ATermMap::hash2(ATerm key) const
+unsigned long ATermMap::hash2(ATerm key) const
 {
-    unsigned int key2 = ((unsigned int) key) >> 2;
+    unsigned long key2 = ((unsigned long) key) >> 2;
     /* Note: the result must be relatively prime to `capacity' (which
        is a power of 2), so we make sure that the result is always
        odd. */
-    unsigned int h = ((key2 * 134217689) & (capacity - 1)) | 1;
+    unsigned long h = ((key2 * 134217689) & (capacity - 1)) | 1;
     return h;
 }
 
diff --git a/src/libutil/aterm-map.hh b/src/libutil/aterm-map.hh
index 203b42934a..115ed36cd5 100644
--- a/src/libutil/aterm-map.hh
+++ b/src/libutil/aterm-map.hh
@@ -113,8 +113,8 @@ private:
 
     void copy(KeyValue * elements, unsigned int capacity);
     
-    inline unsigned int hash1(ATerm key) const;
-    inline unsigned int hash2(ATerm key) const;
+    inline unsigned long hash1(ATerm key) const;
+    inline unsigned long hash2(ATerm key) const;
 };
 
 
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 0d970e69e3..4e93464865 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -119,7 +119,7 @@ Path canonPath(const Path & path, bool resolveSymlinks)
 
 Path dirOf(const Path & path)
 {
-    unsigned int pos = path.rfind('/');
+    Path::size_type pos = path.rfind('/');
     if (pos == string::npos)
         throw Error(format("invalid file name: %1%") % path);
     return pos == 0 ? "/" : Path(path, 0, pos);
@@ -128,7 +128,7 @@ Path dirOf(const Path & path)
 
 string baseNameOf(const Path & path)
 {
-    unsigned int pos = path.rfind('/');
+    Path::size_type pos = path.rfind('/');
     if (pos == string::npos)
         throw Error(format("invalid file name %1% ") % path);
     return string(path, pos + 1);
diff --git a/src/nix-env/main.cc b/src/nix-env/main.cc
index e7f25c5ba2..560612825b 100644
--- a/src/nix-env/main.cc
+++ b/src/nix-env/main.cc
@@ -350,7 +350,7 @@ static void queryInstSources(EvalState & state,
                 DrvInfo elem;
                 elem.attrs = shared_ptr<ATermMap>(new ATermMap(0)); /* ugh... */
                 string name = baseNameOf(*i);
-                unsigned int dash = name.find('-');
+                string::size_type dash = name.find('-');
                 if (dash != string::npos)
                     name = string(name, dash + 1);
 
diff --git a/src/nix-env/profiles.cc b/src/nix-env/profiles.cc
index 6db291b3d2..6ec12e604c 100644
--- a/src/nix-env/profiles.cc
+++ b/src/nix-env/profiles.cc
@@ -19,7 +19,7 @@ static int parseName(const string & profileName, const string & name)
 {
     if (string(name, 0, profileName.size() + 1) != profileName + "-") return -1;
     string s = string(name, profileName.size() + 1);
-    unsigned int p = s.find("-link");
+    string::size_type p = s.find("-link");
     if (p == string::npos) return -1;
     int n;
     if (string2Int(string(s, 0, p), n) && n >= 0)