diff --git a/libutils/tests/Looper_test.cpp b/libutils/tests/Looper_test.cpp
index 00077e6..bdb1bb7 100644
--- a/libutils/tests/Looper_test.cpp
+++ b/libutils/tests/Looper_test.cpp
@@ -76,7 +76,7 @@
     int fd;
     int events;
 
-    StubCallbackHandler(int nextResult) : nextResult(nextResult),
+    explicit StubCallbackHandler(int nextResult) : nextResult(nextResult),
             callbackCount(0), fd(-1), events(-1) {
     }
 
diff --git a/libutils/tests/StrongPointer_test.cpp b/libutils/tests/StrongPointer_test.cpp
index f46d6d1..323a6f2 100644
--- a/libutils/tests/StrongPointer_test.cpp
+++ b/libutils/tests/StrongPointer_test.cpp
@@ -23,7 +23,7 @@
 
 class Foo : public LightRefBase<Foo> {
 public:
-    Foo(bool* deleted_check) : mDeleted(deleted_check) {
+    explicit Foo(bool* deleted_check) : mDeleted(deleted_check) {
         *mDeleted = false;
     }
 
diff --git a/libutils/tests/TestHelpers.h b/libutils/tests/TestHelpers.h
index d8e985e..6801cd7 100644
--- a/libutils/tests/TestHelpers.h
+++ b/libutils/tests/TestHelpers.h
@@ -60,7 +60,7 @@
     int mDelayMillis;
 
 public:
-    DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
+    explicit DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
 
 protected:
     virtual ~DelayedTask() { }