diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 0a6ebcd5c..eb0b53628 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -139,6 +139,10 @@ static void initAndRun(int argc, char * * argv)
 
     /* ATerm stuff.  !!! find a better place to put this */
     initDerivationsHelpers();
+
+    /* Random number generator needed by makeRandomStorePath(); !!!
+       improve. */
+    srand(time(0));
     
     /* Put the arguments in a vector. */
     Strings args, remaining;
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 0b32641f0..f08e4a4d7 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -914,7 +914,7 @@ bool DerivationGoal::prepareBuild()
         rewrites[hashPartOf(i->second.eqClass)] = hashPartOf(tmpPath);
         tmpOutputs[i->second.eqClass] = tmpPath;
     }
-    
+
     /* Obtain locks on all output paths.  The locks are automatically
        released when we exit this function or Nix crashes. */
     /* !!! BUG: this could block, which is not allowed. */
@@ -959,6 +959,7 @@ bool DerivationGoal::prepareBuild()
         debug(format("building path `%1%'") % i->second.path);
         allPaths.insert(i->second.path);
     }
+#endif    
 
     /* Determine the full set of input paths. */
 
@@ -973,9 +974,25 @@ bool DerivationGoal::prepareBuild()
         Derivation inDrv = derivationFromPath(i->first);
         for (StringSet::iterator j = i->second.begin();
              j != i->second.end(); ++j)
-            if (inDrv.outputs.find(*j) != inDrv.outputs.end())
+            
+            if (inDrv.outputs.find(*j) != inDrv.outputs.end()) {
+                
+                OutputEqClass eqClass = inDrv.outputs[*j].eqClass;
+                OutputEqMembers members;
+                queryOutputEqMembers(noTxn, eqClass, members);
+
+                if (members.size() == 0)
+                    throw Error(format("output equivalence class `%1%' has no members!")
+                        % eqClass);
+
+                Path input = members.front().path;
+
+                rewrites[hashPartOf(eqClass)] = hashPartOf(input);
+                    
+#if 0                
                 computeFSClosure(inDrv.outputs[*j].path, inputPaths);
-            else
+#endif
+            } else
                 throw Error(
                     format("derivation `%1%' requires non-existent output `%2%' from input derivation `%3%'")
                     % drvPath % *j % i->first);
@@ -989,7 +1006,6 @@ bool DerivationGoal::prepareBuild()
     debug(format("added input paths %1%") % showPaths(inputPaths));
 
     allPaths.insert(inputPaths.begin(), inputPaths.end());
-#endif    
 
     return true;
 }
@@ -1144,6 +1160,15 @@ void DerivationGoal::computeClosure()
         Path finalPath = addToStore(i->second, hashPartOf(i->second),
             namePartOf(i->second));
         printMsg(lvlError, format("produced final path `%1%'") % finalPath);
+
+        /* Register the fact that this output path is a member of some
+           output path equivalence class (for a certain user, at
+           least).  This is how subsequent derivations will be able to
+           find it. */
+        Transaction txn;
+        createStoreTransaction(txn);
+        addOutputEqMember(txn, i->first, "root", finalPath);
+        txn.commit();
     }
     
 #if 0    
diff --git a/src/libstore/store.cc b/src/libstore/store.cc
index 0cba16b6d..fb9196db8 100644
--- a/src/libstore/store.cc
+++ b/src/libstore/store.cc
@@ -448,10 +448,52 @@ void queryReferers(const Transaction & txn,
 }
 
 
+void addOutputEqMember(const Transaction & txn,
+    const OutputEqClass & eqClass, const TrustId & trustId,
+    const Path & path)
+{
+    OutputEqMembers members;
+    queryOutputEqMembers(txn, eqClass, members);
+
+    for (OutputEqMembers::iterator i = members.begin();
+         i != members.end(); ++i)
+        if (i->trustId == trustId && i->path == path) return;
+    
+    OutputEqMember member;
+    member.trustId = trustId;
+    member.path = path;
+    members.push_back(member);
+
+    Strings ss;
+    
+    for (OutputEqMembers::iterator i = members.begin();
+         i != members.end(); ++i)
+    {
+        Strings ss2;
+        ss2.push_back(i->trustId);
+        ss2.push_back(i->path);
+        ss.push_back(packStrings(ss2));
+    }
+
+    nixDB.setStrings(txn, dbEquivalences, eqClass, ss);
+}
+
+
 void queryOutputEqMembers(const Transaction & txn,
     const OutputEqClass & eqClass, OutputEqMembers & members)
 {
-    assert(0);
+    Strings ss;
+    nixDB.queryStrings(txn, dbEquivalences, eqClass, ss);
+
+    for (Strings::iterator i = ss.begin(); i != ss.end(); ++i) {
+        Strings ss2 = unpackStrings(*i);
+        if (ss2.size() != 2) continue;
+        Strings::iterator j = ss2.begin();
+        OutputEqMember member;
+        member.trustId = *j++;
+        member.path = *j++;
+        members.push_back(member);
+    }
 }
 
 
diff --git a/src/libstore/store.hh b/src/libstore/store.hh
index da5769bef..6d14e6ea9 100644
--- a/src/libstore/store.hh
+++ b/src/libstore/store.hh
@@ -187,6 +187,10 @@ void queryReferences(const Transaction & txn,
 void queryReferers(const Transaction & txn,
     const Path & storePath, PathSet & referers);
 
+void addOutputEqMember(const Transaction & txn,
+    const OutputEqClass & eqClass, const TrustId & trustId,
+    const Path & path);
+
 void queryOutputEqMembers(const Transaction & txn,
     const OutputEqClass & eqClass, OutputEqMembers & members);