diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 4af76a7..faf7f40 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -65,6 +65,9 @@
    default. It warns about unguarded uses of APIs only when they were introduced
    in or after macOS 10.13, iOS 11, tvOS 11 or watchOS 4.
 
+- ``-Wzero-as-null-pointer-constant`` was adjusted not to warn on null pointer
+  constants that originate from system macros, except ``NULL`` macro.
+
 -  The ``-Wdocumentation`` warning now allows the use of ``\param`` and
    ``\returns`` documentation directives in the documentation comments for
    declarations with a function or a block pointer type.
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 6f22620..7f627a3 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -389,14 +389,26 @@
 }
 
 void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr* E) {
-  if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer)
-    return;
-  if (E->getType()->isNullPtrType())
+  if (Diags.isIgnored(diag::warn_zero_as_null_pointer_constant,
+                      E->getLocStart()))
     return;
   // nullptr only exists from C++11 on, so don't warn on its absence earlier.
   if (!getLangOpts().CPlusPlus11)
     return;
 
+  if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer)
+    return;
+  if (E->IgnoreParenImpCasts()->getType()->isNullPtrType())
+    return;
+
+  // If it is a macro from system header, and if the macro name is not "NULL",
+  // do not warn.
+  SourceLocation MaybeMacroLoc = E->getLocStart();
+  if (Diags.getSuppressSystemWarnings() &&
+      SourceMgr.isInSystemMacro(MaybeMacroLoc) &&
+      !findMacroSpelling(MaybeMacroLoc, "NULL"))
+    return;
+
   Diag(E->getLocStart(), diag::warn_zero_as_null_pointer_constant)
       << FixItHint::CreateReplacement(E->getSourceRange(), "nullptr");
 }
diff --git a/test/SemaCXX/Inputs/warn-zero-nullptr.h b/test/SemaCXX/Inputs/warn-zero-nullptr.h
new file mode 100644
index 0000000..9b86c4b
--- /dev/null
+++ b/test/SemaCXX/Inputs/warn-zero-nullptr.h
@@ -0,0 +1,3 @@
+#define NULL (0)
+#define SYSTEM_MACRO (0)
+#define OTHER_SYSTEM_MACRO (NULL)
diff --git a/test/SemaCXX/warn-zero-nullptr.cpp b/test/SemaCXX/warn-zero-nullptr.cpp
index edd2a75..45f05fa 100644
--- a/test/SemaCXX/warn-zero-nullptr.cpp
+++ b/test/SemaCXX/warn-zero-nullptr.cpp
@@ -1,4 +1,10 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s -Wzero-as-null-pointer-constant -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -isystem %S/Inputs -Wzero-as-null-pointer-constant -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -isystem %S/Inputs -DSYSTEM_WARNINGS -Wzero-as-null-pointer-constant -Wsystem-headers -std=c++11
+
+#include <warn-zero-nullptr.h>
+
+#define MACRO (0)
+#define MCRO(x) (x)
 
 struct S {};
 
@@ -15,8 +21,12 @@
 void (*fp2)() = __null; // expected-warning{{zero as null pointer constant}}
 int (S::*mp2) = __null; // expected-warning{{zero as null pointer constant}}
 
-void f0(void* v = 0); // expected-warning{{zero as null pointer constant}}
-void f1(void* v);
+void f0(void* v = MACRO); // expected-warning{{zero as null pointer constant}}
+void f1(void* v = NULL); // expected-warning{{zero as null pointer constant}}
+void f2(void* v = MCRO(0)); // expected-warning{{zero as null pointer constant}}
+void f3(void* v = MCRO(NULL)); // expected-warning{{zero as null pointer constant}}
+void f4(void* v = 0); // expected-warning{{zero as null pointer constant}}
+void f5(void* v);
 
 void g() {
   f1(0); // expected-warning{{zero as null pointer constant}}
@@ -25,3 +35,58 @@
 // Warn on these too. Matches gcc and arguably makes sense.
 void* pp = (decltype(nullptr))0; // expected-warning{{zero as null pointer constant}}
 void* pp2 = static_cast<decltype(nullptr)>(0); // expected-warning{{zero as null pointer constant}}
+
+// Shouldn't warn.
+namespace pr34362 {
+struct A { operator int*() { return nullptr; } };
+void func() { if (nullptr == A()) {} }
+void func2() { if ((nullptr) == A()) {} }
+}
+
+template <typename T> void TmplFunc0(T var) {}
+void Func0Test() {
+  TmplFunc0<int>(0);
+  TmplFunc0<int*>(0); // expected-warning {{zero as null pointer constant}}
+  TmplFunc0<void*>(0); // expected-warning {{zero as null pointer constant}}
+}
+
+// FIXME: this one probably should not warn.
+template <typename T> void TmplFunc1(int a, T default_value = 0) {} // expected-warning{{zero as null pointer constant}} expected-warning{{zero as null pointer constant}}
+void FuncTest() {
+  TmplFunc1<int>(0);
+  TmplFunc1<int*>(0); // expected-note {{in instantiation of default function argument expression for 'TmplFunc1<int *>' required here}}
+  TmplFunc1<void*>(0);  // expected-note {{in instantiation of default function argument expression for 'TmplFunc1<void *>' required here}}
+}
+
+template<typename T>
+class TemplateClass0 {
+ public:
+  explicit TemplateClass0(T var) {}
+};
+void TemplateClass0Test() {
+  TemplateClass0<int> a(0);
+  TemplateClass0<int*> b(0); // expected-warning {{zero as null pointer constant}}
+  TemplateClass0<void*> c(0); // expected-warning {{zero as null pointer constant}}
+}
+
+template<typename T>
+class TemplateClass1 {
+ public:
+// FIXME: this one should *NOT* warn.
+  explicit TemplateClass1(int a, T default_value = 0) {} // expected-warning{{zero as null pointer constant}} expected-warning{{zero as null pointer constant}}
+};
+void IgnoreSubstTemplateType1() {
+  TemplateClass1<int> a(1);
+  TemplateClass1<int*> b(1); // expected-note {{in instantiation of default function argument expression for 'TemplateClass1<int *>' required here}}
+  TemplateClass1<void*> c(1); // expected-note {{in instantiation of default function argument expression for 'TemplateClass1<void *>' required here}}
+}
+
+#ifndef SYSTEM_WARNINGS
+// Do not warn on *any* other macros from system headers, even if they
+// expand to/their expansion contains NULL.
+void* sys_init = SYSTEM_MACRO;
+void* sys_init2 = OTHER_SYSTEM_MACRO;
+#else
+void* sys_init = SYSTEM_MACRO; // expected-warning {{zero as null pointer constant}}
+void* sys_init2 = OTHER_SYSTEM_MACRO; // expected-warning {{zero as null pointer constant}}
+#endif