diff --git a/tests/keymaster/keymaster_test.cpp b/tests/keymaster/keymaster_test.cpp
index 6266d40..3040a5c 100644
--- a/tests/keymaster/keymaster_test.cpp
+++ b/tests/keymaster/keymaster_test.cpp
@@ -41,7 +41,7 @@
 
 class UniqueBlob : public UniquePtr<uint8_t[]> {
 public:
-    UniqueBlob(size_t length) :
+    explicit UniqueBlob(size_t length) :
             mLength(length) {
     }