diff --git a/src/libstore/nar-info-disk-cache.cc b/src/libstore/nar-info-disk-cache.cc
index 8541cc51f..1d8d2d57e 100644
--- a/src/libstore/nar-info-disk-cache.cc
+++ b/src/libstore/nar-info-disk-cache.cc
@@ -109,8 +109,10 @@ public:
                 SQLiteStmt(state->db,
                     "delete from NARs where ((present = 0 and timestamp < ?) or (present = 1 and timestamp < ?))")
                     .use()
-                    (now - settings.ttlNegativeNarInfoCache)
-                    (now - settings.ttlPositiveNarInfoCache)
+                    // Use a minimum TTL to prevent --refresh from
+                    // nuking the entire disk cache.
+                    (now - std::max(settings.ttlNegativeNarInfoCache.get(), 3600U))
+                    (now - std::max(settings.ttlPositiveNarInfoCache.get(), 30 * 24 * 3600U))
                     .exec();
 
                 debug("deleted %d entries from the NAR info disk cache", sqlite3_changes(state->db));
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 418396280..80422bd24 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -330,8 +330,11 @@ void mainWrapped(int argc, char * * argv)
             fileTransferSettings.connectTimeout = 1;
     }
 
-    if (args.refresh)
+    if (args.refresh) {
         settings.tarballTtl = 0;
+        settings.ttlNegativeNarInfoCache = 0;
+        settings.ttlPositiveNarInfoCache = 0;
+    }
 
     args.command->second->prepare();
     args.command->second->run();