diff --git a/src/limitedmap.h b/src/limitedmap.h
index b990eab3e..5456dfc7c 100644
--- a/src/limitedmap.h
+++ b/src/limitedmap.h
@@ -27,7 +27,11 @@ protected:
     size_type nMaxSize;
 
 public:
-    limitedmap(size_type nMaxSizeIn = 0) { nMaxSize = nMaxSizeIn; }
+    limitedmap(size_type nMaxSizeIn)
+    {
+        assert(nMaxSizeIn > 0);
+        nMaxSize = nMaxSizeIn;
+    }
     const_iterator begin() const { return map.begin(); }
     const_iterator end() const { return map.end(); }
     size_type size() const { return map.size(); }
@@ -38,13 +42,12 @@ public:
     {
         std::pair<iterator, bool> ret = map.insert(x);
         if (ret.second) {
-            if (nMaxSize && map.size() > nMaxSize) {
+            if (map.size() > nMaxSize) {
                 map.erase(rmap.begin()->second);
                 rmap.erase(rmap.begin());
             }
             rmap.insert(make_pair(x.second, ret.first));
         }
-        return;
     }
     void erase(const key_type& k)
     {
@@ -81,11 +84,11 @@ public:
     size_type max_size() const { return nMaxSize; }
     size_type max_size(size_type s)
     {
-        if (s)
-            while (map.size() > s) {
-                map.erase(rmap.begin()->second);
-                rmap.erase(rmap.begin());
-            }
+        assert(s > 0);
+        while (map.size() > s) {
+            map.erase(rmap.begin()->second);
+            rmap.erase(rmap.begin());
+        }
         nMaxSize = s;
         return nMaxSize;
     }