diff --git a/libc/bionic/system_properties.cpp b/libc/bionic/system_properties.cpp
index 9c992da..0f68431 100644
--- a/libc/bionic/system_properties.cpp
+++ b/libc/bionic/system_properties.cpp
@@ -192,7 +192,7 @@
     const uint32_t n;
     const prop_info *pi;
 
-    find_nth_cookie(uint32_t n) : count(0), n(n), pi(NULL) {
+    explicit find_nth_cookie(uint32_t n) : count(0), n(n), pi(NULL) {
     }
 };