diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index ea1e4db..22162fa 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -71,7 +71,7 @@
 
 #if !DEBUG_REFS
 
-    weakref_impl(RefBase* base)
+    explicit weakref_impl(RefBase* base)
         : mStrong(INITIAL_STRONG_VALUE)
         , mWeak(0)
         , mBase(base)