diff --git a/build/clang-plugin/clang-plugin.cpp b/build/clang-plugin/clang-plugin.cpp
index ec9ece09689..0999789d44e 100644
--- a/build/clang-plugin/clang-plugin.cpp
+++ b/build/clang-plugin/clang-plugin.cpp
@@ -84,11 +84,6 @@ private:
     virtual void run(const MatchFinder::MatchResult &Result);
   };
 
-  class ExplicitOperatorBoolChecker : public MatchFinder::MatchCallback {
-  public:
-    virtual void run(const MatchFinder::MatchResult &Result);
-  };
-
   ScopeChecker stackClassChecker;
   ScopeChecker globalClassChecker;
   NonHeapClassChecker nonheapClassChecker;
@@ -97,17 +92,16 @@ private:
   NaNExprChecker nanExprChecker;
   NoAddRefReleaseOnReturnChecker noAddRefReleaseOnReturnChecker;
   RefCountedInsideLambdaChecker refCountedInsideLambdaChecker;
-  ExplicitOperatorBoolChecker explicitOperatorBoolChecker;
   MatchFinder astMatcher;
 };
 
 namespace {
 
-std::string getDeclarationNamespace(const Decl *decl) {
+bool isInIgnoredNamespace(const Decl *decl) {
   const DeclContext *DC = decl->getDeclContext()->getEnclosingNamespaceContext();
   const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(DC);
   if (!ND) {
-    return "";
+    return false;
   }
 
   while (const DeclContext *ParentDC = ND->getParent()) {
@@ -118,15 +112,8 @@ std::string getDeclarationNamespace(const Decl *decl) {
   }
 
   const auto& name = ND->getName();
-  return name;
-}
-
-bool isInIgnoredNamespaceForImplicitCtor(const Decl *decl) {
-  std::string name = getDeclarationNamespace(decl);
-  if (name == "") {
-    return false;
-  }
 
+  // namespace std and icu are ignored for now
   return name == "std" ||              // standard C++ lib
          name == "__gnu_cxx" ||        // gnu C++ lib
          name == "boost" ||            // boost
@@ -142,19 +129,7 @@ bool isInIgnoredNamespaceForImplicitCtor(const Decl *decl) {
          name == "testing";            // gtest
 }
 
-bool isInIgnoredNamespaceForImplicitConversion(const Decl *decl) {
-  std::string name = getDeclarationNamespace(decl);
-  if (name == "") {
-    return false;
-  }
-
-  return name == "std" ||              // standard C++ lib
-         name == "__gnu_cxx" ||        // gnu C++ lib
-         name == "google_breakpad" ||  // breakpad
-         name == "testing";            // gtest
-}
-
-bool isIgnoredPathForImplicitCtor(const Decl *decl) {
+bool isIgnoredPath(const Decl *decl) {
   decl = decl->getCanonicalDecl();
   SourceLocation Loc = decl->getLocation();
   const SourceManager &SM = decl->getASTContext().getSourceManager();
@@ -175,30 +150,9 @@ bool isIgnoredPathForImplicitCtor(const Decl *decl) {
   return false;
 }
 
-bool isIgnoredPathForImplicitConversion(const Decl *decl) {
-  decl = decl->getCanonicalDecl();
-  SourceLocation Loc = decl->getLocation();
-  const SourceManager &SM = decl->getASTContext().getSourceManager();
-  SmallString<1024> FileName = SM.getFilename(Loc);
-  llvm::sys::fs::make_absolute(FileName);
-  llvm::sys::path::reverse_iterator begin = llvm::sys::path::rbegin(FileName),
-                                    end   = llvm::sys::path::rend(FileName);
-  for (; begin != end; ++begin) {
-    if (begin->compare_lower(StringRef("graphite2")) == 0) {
-      return true;
-    }
-  }
-  return false;
-}
-
-bool isInterestingDeclForImplicitCtor(const Decl *decl) {
-  return !isInIgnoredNamespaceForImplicitCtor(decl) &&
-         !isIgnoredPathForImplicitCtor(decl);
-}
-
-bool isInterestingDeclForImplicitConversion(const Decl *decl) {
-  return !isInIgnoredNamespaceForImplicitConversion(decl) &&
-         !isIgnoredPathForImplicitConversion(decl);
+bool isInterestingDecl(const Decl *decl) {
+  return !isInIgnoredNamespace(decl) &&
+         !isIgnoredPath(decl);
 }
 
 }
@@ -278,7 +232,7 @@ public:
       }
     }
 
-    if (!d->isAbstract() && isInterestingDeclForImplicitCtor(d)) {
+    if (!d->isAbstract() && isInterestingDecl(d)) {
       for (CXXRecordDecl::ctor_iterator ctor = d->ctor_begin(),
            e = d->ctor_end(); ctor != e; ++ctor) {
         // Ignore non-converting ctors
@@ -462,16 +416,6 @@ bool isClassRefCounted(QualType T) {
   return clazz ? isClassRefCounted(clazz) : RegularClass;
 }
 
-template<class T>
-bool IsInSystemHeader(const ASTContext &AC, const T &D) {
-  auto &SourceManager = AC.getSourceManager();
-  auto ExpansionLoc = SourceManager.getExpansionLoc(D.getLocStart());
-  if (ExpansionLoc.isInvalid()) {
-    return false;
-  }
-  return SourceManager.isInSystemHeader(ExpansionLoc);
-}
-
 }
 
 namespace clang {
@@ -571,7 +515,12 @@ AST_MATCHER(QualType, isFloat) {
 /// isExpansionInSystemHeader in newer clangs, but modified in order to work
 /// with old clangs that we use on infra.
 AST_MATCHER(BinaryOperator, isInSystemHeader) {
-  return IsInSystemHeader(Finder->getASTContext(), Node);
+  auto &SourceManager = Finder->getASTContext().getSourceManager();
+  auto ExpansionLoc = SourceManager.getExpansionLoc(Node.getLocStart());
+  if (ExpansionLoc.isInvalid()) {
+    return false;
+  }
+  return SourceManager.isInSystemHeader(ExpansionLoc);
 }
 
 /// This matcher will match locations in SkScalar.h.  This header contains a
@@ -700,13 +649,6 @@ DiagnosticsMatcher::DiagnosticsMatcher()
             hasDescendant(declRefExpr(hasType(pointerType(pointee(isRefCounted())))).bind("node"))
         ),
     &refCountedInsideLambdaChecker);
-
-  // Older clang versions such as the ones used on the infra recognize these
-  // conversions as 'operator _Bool', but newer clang versions recognize these
-  // as 'operator bool'.
-  astMatcher.addMatcher(methodDecl(anyOf(hasName("operator bool"),
-                                         hasName("operator _Bool"))).bind("node"),
-    &explicitOperatorBoolChecker);
 }
 
 void DiagnosticsMatcher::ScopeChecker::run(
@@ -919,25 +861,6 @@ void DiagnosticsMatcher::RefCountedInsideLambdaChecker::run(
   Diag.Report(node->getLocStart(), noteID);
 }
 
-void DiagnosticsMatcher::ExplicitOperatorBoolChecker::run(
-    const MatchFinder::MatchResult &Result) {
-  DiagnosticsEngine &Diag = Result.Context->getDiagnostics();
-  unsigned errorID = Diag.getDiagnosticIDs()->getCustomDiagID(
-      DiagnosticIDs::Error, "bad implicit conversion operator for %0");
-  unsigned noteID = Diag.getDiagnosticIDs()->getCustomDiagID(
-      DiagnosticIDs::Note, "consider adding the explicit keyword to %0");
-  const CXXConversionDecl *method = Result.Nodes.getNodeAs<CXXConversionDecl>("node");
-  const CXXRecordDecl *clazz = method->getParent();
-
-  if (!method->isExplicitSpecified() &&
-      !MozChecker::hasCustomAnnotation(method, "moz_implicit") &&
-      !IsInSystemHeader(method->getASTContext(), *method) &&
-      isInterestingDeclForImplicitConversion(method)) {
-    Diag.Report(method->getLocStart(), errorID) << clazz;
-    Diag.Report(method->getLocStart(), noteID) << "'operator bool'";
-  }
-}
-
 class MozCheckAction : public PluginASTAction {
 public:
   ASTConsumerPtr CreateASTConsumer(CompilerInstance &CI, StringRef fileName) override {
diff --git a/build/clang-plugin/tests/TestExplicitOperatorBool.cpp b/build/clang-plugin/tests/TestExplicitOperatorBool.cpp
deleted file mode 100644
index bc4b43a7d06..00000000000
--- a/build/clang-plugin/tests/TestExplicitOperatorBool.cpp
+++ /dev/null
@@ -1,11 +0,0 @@
-#define MOZ_IMPLICIT __attribute__((annotate("moz_implicit")))
-
-struct Bad {
-  operator bool(); // expected-error {{bad implicit conversion operator for 'Bad'}} expected-note {{consider adding the explicit keyword to 'operator bool'}}
-};
-struct Good {
-  explicit operator bool();
-};
-struct Okay {
-  MOZ_IMPLICIT operator bool();
-};
diff --git a/build/clang-plugin/tests/moz.build b/build/clang-plugin/tests/moz.build
index 0894046e112..5a6a26b5034 100644
--- a/build/clang-plugin/tests/moz.build
+++ b/build/clang-plugin/tests/moz.build
@@ -7,7 +7,6 @@
 SOURCES += [
     'TestBadImplicitConversionCtor.cpp',
     'TestCustomHeap.cpp',
-    'TestExplicitOperatorBool.cpp',
     'TestGlobalClass.cpp',
     'TestMustOverride.cpp',
     'TestNANTestingExpr.cpp',
diff --git a/dom/bindings/CallbackObject.h b/dom/bindings/CallbackObject.h
index a07279e96bc..5d8565e9c31 100644
--- a/dom/bindings/CallbackObject.h
+++ b/dom/bindings/CallbackObject.h
@@ -305,7 +305,7 @@ public:
   }
 
   // Boolean conversion operator so people can use this in boolean tests
-  explicit operator bool() const
+  operator bool() const
   {
     return GetISupports();
   }
diff --git a/dom/html/HTMLMediaElement.h b/dom/html/HTMLMediaElement.h
index cec21baefa6..b5e6a66dd66 100644
--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -660,7 +660,7 @@ protected:
     void SetOuter(HTMLMediaElement* outer) { mOuter = outer; }
     void SetCanPlay(bool aCanPlay);
 
-    MOZ_IMPLICIT operator bool() const { return mValue; }
+    operator bool() const { return mValue; }
 
     WakeLockBoolWrapper& operator=(bool val);
 
diff --git a/dom/media/SelfRef.h b/dom/media/SelfRef.h
index 301d986fa0d..866b6de9953 100644
--- a/dom/media/SelfRef.h
+++ b/dom/media/SelfRef.h
@@ -35,7 +35,7 @@ public:
     }
   }
 
-  MOZ_IMPLICIT operator bool() const { return mHeld; }
+  operator bool() const { return mHeld; }
 
   SelfReference(const SelfReference& aOther) = delete;
   void operator=(const SelfReference& aOther) = delete;
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.cpp b/dom/plugins/base/nsNPAPIPluginInstance.cpp
index efcc353682e..5f601403b16 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -1167,7 +1167,7 @@ public:
     if (plugin)
       mLibrary = plugin->GetLibrary();
   }
-  explicit operator bool() { return !!mLibrary; }
+  operator bool() { return !!mLibrary; }
   PluginLibrary* operator->() { return mLibrary; }
 
 private:
diff --git a/dom/plugins/ipc/PluginScriptableObjectUtils.h b/dom/plugins/ipc/PluginScriptableObjectUtils.h
index bef2113c79f..432c53b7777 100644
--- a/dom/plugins/ipc/PluginScriptableObjectUtils.h
+++ b/dom/plugins/ipc/PluginScriptableObjectUtils.h
@@ -277,7 +277,7 @@ public:
     return mActor;
   }
 
-  explicit operator bool()
+  operator bool()
   {
     return !!mActor;
   }
diff --git a/hal/linux/udev.h b/hal/linux/udev.h
index 4c717560c03..9f28d95c827 100644
--- a/hal/linux/udev.h
+++ b/hal/linux/udev.h
@@ -63,7 +63,7 @@ class udev_lib {
     }
   }
 
-  explicit operator bool() {
+  operator bool() {
     return udev;
   }
 
diff --git a/memory/replace/logalloc/replay/Replay.cpp b/memory/replace/logalloc/replay/Replay.cpp
index a047d4152bf..75db8fb1e76 100644
--- a/memory/replace/logalloc/replay/Replay.cpp
+++ b/memory/replace/logalloc/replay/Replay.cpp
@@ -176,7 +176,7 @@ public:
   }
 
   /* Returns whether the buffer is empty. */
-  explicit operator bool() { return mLength; }
+  operator bool() { return mLength; }
 
   /* Returns the memory location of the buffer. */
   const char* get() { return mBuf; }
diff --git a/mfbt/Atomics.h b/mfbt/Atomics.h
index 33610144eda..0afee7f2df5 100644
--- a/mfbt/Atomics.h
+++ b/mfbt/Atomics.h
@@ -742,7 +742,7 @@ public:
   explicit MOZ_CONSTEXPR Atomic(bool aInit) : Base(aInit) {}
 
   // We provide boolean wrappers for the underlying AtomicBase methods.
-  MOZ_IMPLICIT operator bool() const
+  operator bool() const
   {
     return Base::Intrinsics::load(Base::mValue);
   }
diff --git a/netwerk/base/AutoClose.h b/netwerk/base/AutoClose.h
index f8521144a9d..ba82614f69d 100644
--- a/netwerk/base/AutoClose.h
+++ b/netwerk/base/AutoClose.h
@@ -23,7 +23,7 @@ public:
     Close();
   }
 
-  explicit operator bool() const
+  operator bool() const
   {
     return mPtr;
   }
diff --git a/netwerk/socket/nsSOCKSIOLayer.cpp b/netwerk/socket/nsSOCKSIOLayer.cpp
index d07df13ecf2..50232f0f590 100644
--- a/netwerk/socket/nsSOCKSIOLayer.cpp
+++ b/netwerk/socket/nsSOCKSIOLayer.cpp
@@ -242,7 +242,7 @@ public:
       return mLength;
   }
 
-  explicit operator bool() { return !!mBuf; }
+  operator bool() { return !!mBuf; }
 private:
   template <size_t Size2>
   friend class Buffer;
diff --git a/xpcom/build/FileLocation.h b/xpcom/build/FileLocation.h
index 17f24be6f33..967718b0ee6 100644
--- a/xpcom/build/FileLocation.h
+++ b/xpcom/build/FileLocation.h
@@ -90,9 +90,9 @@ public:
    * or not.
    */
 #if defined(MOZILLA_XPCOMRT_API)
-  explicit operator bool() const { return mBaseFile; }
+  operator bool() const { return mBaseFile; }
 #else
-  explicit operator bool() const { return mBaseFile || mBaseZip; }
+  operator bool() const { return mBaseFile || mBaseZip; }
 #endif // defined(MOZILLA_XPCOMRT_API)
 
   /**
diff --git a/xpcom/glue/nsTArray.h b/xpcom/glue/nsTArray.h
index 9d654d54bcb..c7f56614a8e 100644
--- a/xpcom/glue/nsTArray.h
+++ b/xpcom/glue/nsTArray.h
@@ -112,7 +112,7 @@ struct nsTArrayFallibleResult
   // Note: allows implicit conversions from and to bool
   MOZ_IMPLICIT nsTArrayFallibleResult(bool aResult) : mResult(aResult) {}
 
-  MOZ_IMPLICIT operator bool() { return mResult; }
+  operator bool() { return mResult; }
 
 private:
   bool mResult;