diff --git a/include/univalue.h b/include/univalue.h
index 8f671888b52974..4efc64aba211f5 100644
--- a/include/univalue.h
+++ b/include/univalue.h
@@ -72,7 +72,7 @@ class UniValue {
     bool checkObject(const std::map<std::string,UniValue::VType>& memberTypes);
     const UniValue& operator[](const std::string& key) const;
     const UniValue& operator[](unsigned int index) const;
-    bool exists(const std::string& key) const { return (findKey(key) >= 0); }
+    bool exists(const std::string& key) const { size_t i; return findKey(key, i); }
 
     bool isNull() const { return (typ == VNULL); }
     bool isTrue() const { return (typ == VBOOL) && (val == "1"); }
@@ -148,7 +148,7 @@ class UniValue {
     std::vector<std::string> keys;
     std::vector<UniValue> values;
 
-    int findKey(const std::string& key) const;
+    bool findKey(const std::string& key, size_t& retIdx) const;
     void writeArray(unsigned int prettyIndent, unsigned int indentLevel, std::string& s) const;
     void writeObject(unsigned int prettyIndent, unsigned int indentLevel, std::string& s) const;
 
diff --git a/lib/univalue.cpp b/lib/univalue.cpp
index 6058622a549c87..a973d2680cc630 100644
--- a/lib/univalue.cpp
+++ b/lib/univalue.cpp
@@ -212,22 +212,24 @@ bool UniValue::pushKVs(const UniValue& obj)
     return true;
 }
 
-int UniValue::findKey(const std::string& key) const
+bool UniValue::findKey(const std::string& key, size_t& retIdx) const
 {
-    for (unsigned int i = 0; i < keys.size(); i++) {
-        if (keys[i] == key)
-            return (int) i;
+    for (size_t i = 0; i < keys.size(); i++) {
+        if (keys[i] == key) {
+            retIdx = i;
+            return true;
+        }
     }
 
-    return -1;
+    return false;
 }
 
 bool UniValue::checkObject(const std::map<std::string,UniValue::VType>& t)
 {
     for (std::map<std::string,UniValue::VType>::const_iterator it = t.begin();
          it != t.end(); ++it) {
-        int idx = findKey(it->first);
-        if (idx < 0)
+        size_t idx = 0;
+        if (!findKey(it->first, idx))
             return false;
 
         if (values.at(idx).getType() != it->second)
@@ -242,8 +244,8 @@ const UniValue& UniValue::operator[](const std::string& key) const
     if (typ != VOBJ)
         return NullUniValue;
 
-    int index = findKey(key);
-    if (index < 0)
+    size_t index = 0;
+    if (!findKey(key, index))
         return NullUniValue;
 
     return values.at(index);