diff --git a/libc/bionic/icu.cpp b/libc/bionic/icu.cpp
index 78e551b..c09c9ea 100644
--- a/libc/bionic/icu.cpp
+++ b/libc/bionic/icu.cpp
@@ -68,7 +68,7 @@
   }
   free(namelist);
 
-  if (max_version == -1 || max_version < ICUDATA_VERSION_MIN) {
+  if (max_version < ICUDATA_VERSION_MIN) {
     async_safe_write_log(ANDROID_LOG_ERROR, "bionic-icu", "couldn't find an ICU .dat file");
     return false;
   }
diff --git a/libc/malloc_debug/MapData.h b/libc/malloc_debug/MapData.h
index 0238139..895f78f 100644
--- a/libc/malloc_debug/MapData.h
+++ b/libc/malloc_debug/MapData.h
@@ -41,7 +41,7 @@
   MapEntry(uintptr_t start, uintptr_t end, uintptr_t offset, const char* name, size_t name_len)
       : start(start), end(end), offset(offset), name(name, name_len) {}
 
-  MapEntry(uintptr_t pc) : start(pc), end(pc) {}
+  explicit MapEntry(uintptr_t pc) : start(pc), end(pc) {}
 
   uintptr_t start;
   uintptr_t end;
diff --git a/libc/malloc_debug/OptionData.h b/libc/malloc_debug/OptionData.h
index 80190f5..5c2d272 100644
--- a/libc/malloc_debug/OptionData.h
+++ b/libc/malloc_debug/OptionData.h
@@ -34,7 +34,7 @@
 
 class OptionData {
  public:
-  OptionData(DebugData* debug) : debug_(debug) {}
+  explicit OptionData(DebugData* debug) : debug_(debug) {}
   ~OptionData() = default;
 
  protected:
diff --git a/libc/malloc_debug/RecordData.h b/libc/malloc_debug/RecordData.h
index 6e19923..ccabac2 100644
--- a/libc/malloc_debug/RecordData.h
+++ b/libc/malloc_debug/RecordData.h
@@ -66,7 +66,7 @@
 
 class AllocEntry : public RecordEntry {
  public:
-  AllocEntry(void* pointer);
+  explicit AllocEntry(void* pointer);
   virtual ~AllocEntry() = default;
 
  protected:
@@ -92,7 +92,7 @@
 
 class FreeEntry : public AllocEntry {
  public:
-  FreeEntry(void* pointer);
+  explicit FreeEntry(void* pointer);
   virtual ~FreeEntry() = default;
 
   std::string GetString() const override;
diff --git a/libc/malloc_debug/TrackData.h b/libc/malloc_debug/TrackData.h
index f7486e9..9a649b9 100644
--- a/libc/malloc_debug/TrackData.h
+++ b/libc/malloc_debug/TrackData.h
@@ -46,7 +46,7 @@
 
 class TrackData : public OptionData {
  public:
-  TrackData(DebugData* debug_data);
+  explicit TrackData(DebugData* debug_data);
   virtual ~TrackData() = default;
 
   void GetList(std::vector<const Header*>* list);
diff --git a/libc/private/CachedProperty.h b/libc/private/CachedProperty.h
index 84ead01..bd67d74 100644
--- a/libc/private/CachedProperty.h
+++ b/libc/private/CachedProperty.h
@@ -38,7 +38,7 @@
 class CachedProperty {
  public:
   // The lifetime of `property_name` must be greater than that of this CachedProperty.
-  CachedProperty(const char* property_name)
+  explicit CachedProperty(const char* property_name)
     : property_name_(property_name),
       prop_info_(nullptr),
       cached_area_serial_(0),
diff --git a/libc/private/KernelArgumentBlock.h b/libc/private/KernelArgumentBlock.h
index 68d4999..747186c 100644
--- a/libc/private/KernelArgumentBlock.h
+++ b/libc/private/KernelArgumentBlock.h
@@ -32,7 +32,7 @@
 // constituents for easy access.
 class KernelArgumentBlock {
  public:
-  KernelArgumentBlock(void* raw_args) {
+  explicit KernelArgumentBlock(void* raw_args) {
     uintptr_t* args = reinterpret_cast<uintptr_t*>(raw_args);
     argc = static_cast<int>(*args);
     argv = reinterpret_cast<char**>(args + 1);
diff --git a/libc/system_properties/include/system_properties/system_properties.h b/libc/system_properties/include/system_properties/system_properties.h
index c74f875..83ac00c 100644
--- a/libc/system_properties/include/system_properties/system_properties.h
+++ b/libc/system_properties/include/system_properties/system_properties.h
@@ -48,7 +48,7 @@
   SystemProperties() {
   }
   // Special constructor for testing that also zero initializes the important members.
-  SystemProperties(bool initialized) : initialized_(initialized) {
+  explicit SystemProperties(bool initialized) : initialized_(initialized) {
   }
 
   DISALLOW_COPY_AND_ASSIGN(SystemProperties);