diff --git a/hashing/chaining.cpp b/hashing/chaining.cpp
index 5f40b852b..974b10584 100644
--- a/hashing/chaining.cpp
+++ b/hashing/chaining.cpp
@@ -34,7 +34,7 @@ class chain {
      *
      * @param mod modulus of the chain
      */
-    chain(int mod) : _mod(mod) {
+    explicit chain(int mod) : _mod(mod) {
         while (mod--) head.push_back(nullptr);
     }