diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index e84faff..e62b80f 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -945,7 +945,7 @@
 
 class ResolveCatchBlockExceptionsClassVisitor : public ClassVisitor {
  public:
-  ResolveCatchBlockExceptionsClassVisitor(
+  explicit ResolveCatchBlockExceptionsClassVisitor(
       std::set<std::pair<uint16_t, const DexFile*>>& exceptions_to_resolve)
      : exceptions_to_resolve_(exceptions_to_resolve) {}
 
diff --git a/runtime/gc/space/image_space.cc b/runtime/gc/space/image_space.cc
index 1a33d1f..78c570f 100644
--- a/runtime/gc/space/image_space.cc
+++ b/runtime/gc/space/image_space.cc
@@ -880,7 +880,7 @@
 
 class ForwardObjectAdapter {
  public:
-  ALWAYS_INLINE ForwardObjectAdapter(const FixupVisitor* visitor) : visitor_(visitor) {}
+  ALWAYS_INLINE explicit ForwardObjectAdapter(const FixupVisitor* visitor) : visitor_(visitor) {}
 
   template <typename T>
   ALWAYS_INLINE T* operator()(T* src) const {
@@ -893,7 +893,7 @@
 
 class ForwardCodeAdapter {
  public:
-  ALWAYS_INLINE ForwardCodeAdapter(const FixupVisitor* visitor)
+  ALWAYS_INLINE explicit ForwardCodeAdapter(const FixupVisitor* visitor)
       : visitor_(visitor) {}
 
   template <typename T>
diff --git a/runtime/quick_exception_handler.cc b/runtime/quick_exception_handler.cc
index a785ecb..e32f86b 100644
--- a/runtime/quick_exception_handler.cc
+++ b/runtime/quick_exception_handler.cc
@@ -611,7 +611,7 @@
 // Prints out methods with their type of frame.
 class DumpFramesWithTypeStackVisitor FINAL : public StackVisitor {
  public:
-  DumpFramesWithTypeStackVisitor(Thread* self, bool show_details = false)
+  explicit DumpFramesWithTypeStackVisitor(Thread* self, bool show_details = false)
       SHARED_REQUIRES(Locks::mutator_lock_)
       : StackVisitor(self, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
         show_details_(show_details) {}