diff --git a/scripts/download-using-manifests.pl.in b/scripts/download-using-manifests.pl.in
index 8207aaaa4e..c0b822b912 100644
--- a/scripts/download-using-manifests.pl.in
+++ b/scripts/download-using-manifests.pl.in
@@ -8,7 +8,6 @@ use File::Temp qw(tempdir);
 my $manifestDir = "@localstatedir@/nix/manifests";
 my $logFile = "@localstatedir@/log/nix/downloads";
 
-open LOGFILE, ">>$logFile" or die "cannot open log file $logFile";
 
 # Create a temporary directory.
 my $tmpDir = tempdir("nix-download.XXXXXX", CLEANUP => 1, TMPDIR => 1)
@@ -76,6 +75,8 @@ die unless scalar @ARGV == 2;
 my $targetPath = $ARGV[1];
 
 
+open LOGFILE, ">>$logFile" or die "cannot open log file $logFile";
+
 my $date = strftime ("%F %H:%M:%S UTC", gmtime (time));
 print LOGFILE "$$ get $targetPath $date\n";
 
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 105f711228..d886ba5586 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -15,6 +15,7 @@
 #include <unistd.h>
 #include <utime.h>
 #include <fcntl.h>
+#include <errno.h>
 
 
 namespace nix {
@@ -48,8 +49,14 @@ LocalStore::LocalStore()
 
     checkStoreNotSymlink();
 
-    Path globalLockPath = nixDBPath + "/big-lock";
-    globalLock = openLockFile(globalLockPath.c_str(), true);
+    try {
+        Path globalLockPath = nixDBPath + "/big-lock";
+        globalLock = openLockFile(globalLockPath.c_str(), true);
+    } catch (SysError & e) {
+        if (e.errNo != EACCES) throw;
+        readOnlyMode = true;
+        return;
+    }
     
     if (!lockFile(globalLock, ltRead, false)) {
         printMsg(lvlError, "waiting for the big Nix store lock...");
@@ -59,9 +66,6 @@ LocalStore::LocalStore()
     createDirs(nixDBPath + "/info");
     createDirs(nixDBPath + "/referrer");
 
-    //printMsg(lvlTalkative, "cannot access Nix database; continuing anyway");
-    //readOnlyMode = true;
-
     int curSchema = getSchema();
     if (curSchema > nixSchemaVersion)
         throw Error(format("current Nix store schema is version %1%, but I only support %2%")