Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -5820,6 +5820,9 @@
   "taking the address of a destructor">;
 def err_typecheck_unary_expr : Error<
   "invalid argument type %0 to unary expression">;
+def warn_unsignedtypecheck_unary_minus : Warning<
+  "unary minus operator applied to type %0, result value is still unsigned">,
+   InGroup<SignConversion>;
 def err_typecheck_indirection_requires_pointer : Error<
   "indirection requires pointer operand (%0 invalid)">;
 def ext_typecheck_indirection_through_void_pointer : ExtWarn<
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -12646,13 +12646,18 @@
     resultType = Input.get()->getType();
     if (resultType->isDependentType())
       break;
-    if (resultType->isArithmeticType()) // C99 6.5.3.3p1
+    if (resultType->isArithmeticType()) { // C99 6.5.3.3p1
+      if (Opc == UO_Minus && resultType->isUnsignedIntegerType())
+        return Diag(OpLoc, diag::warn_unsignedtypecheck_unary_minus)
+               << resultType << FixItHint::CreateRemoval(OpLoc)
+               << FixItHint::CreateInsertion(InputExpr->getBeginLoc(), "0u - ")
+               << Input.get()->getSourceRange();
       break;
-    else if (resultType->isVectorType() &&
-             // The z vector extensions don't allow + or - with bool vectors.
-             (!Context.getLangOpts().ZVector ||
-              resultType->getAs<VectorType>()->getVectorKind() !=
-              VectorType::AltiVecBool))
+    } else if (resultType->isVectorType() &&
+               // The z vector extensions don't allow + or - with bool vectors.
+               (!Context.getLangOpts().ZVector ||
+                resultType->getAs<VectorType>()->getVectorKind() !=
+                    VectorType::AltiVecBool))
       break;
     else if (getLangOpts().CPlusPlus && // C++ [expr.unary.op]p6
              Opc == UO_Plus &&
Index: test/CXX/drs/dr6xx.cpp
===================================================================
--- test/CXX/drs/dr6xx.cpp
+++ test/CXX/drs/dr6xx.cpp
@@ -91,7 +91,8 @@
   struct D : B, C {};
 }
 
-int dr610[-0u == 0u ? 1 : -1]; // dr610: yes
+int dr610[-0u == 0u ? // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
+  1 : -1]; // dr610: yes
 
 namespace dr611 { // dr611: yes
   int k;
Index: test/OpenMP/teams_distribute_thread_limit_messages.cpp
===================================================================
--- test/OpenMP/teams_distribute_thread_limit_messages.cpp
+++ test/OpenMP/teams_distribute_thread_limit_messages.cpp
@@ -51,7 +51,7 @@
 #pragma omp teams distribute thread_limit(-2) // expected-error {{argument to 'thread_limit' clause must be a strictly positive integer value}}
   for (int j=0; j<100; j++) foo();
 #pragma omp target
-#pragma omp teams distribute thread_limit(-10u)
+#pragma omp teams distribute thread_limit(-10u) // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
   for (int j=0; j<100; j++) foo();
 #pragma omp target
 #pragma omp teams distribute thread_limit(3.14) // expected-error 2 {{expression must have integral or unscoped enumeration type, not 'double'}}
@@ -102,7 +102,7 @@
   for (int j=0; j<100; j++) foo();
 
 #pragma omp target
-#pragma omp teams distribute thread_limit (-10u)
+#pragma omp teams distribute thread_limit (-10u) // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
   for (int j=0; j<100; j++) foo();
 
 #pragma omp target
Index: test/OpenMP/teams_thread_limit_messages.cpp
===================================================================
--- test/OpenMP/teams_thread_limit_messages.cpp
+++ test/OpenMP/teams_thread_limit_messages.cpp
@@ -51,7 +51,7 @@
 #pragma omp teams thread_limit(-2) // expected-error {{argument to 'thread_limit' clause must be a strictly positive integer value}}
   foo();
 #pragma omp target
-#pragma omp teams thread_limit(-10u)
+#pragma omp teams thread_limit(-10u) // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
   foo();
 #pragma omp target
 #pragma omp teams thread_limit(3.14) // expected-error 2 {{expression must have integral or unscoped enumeration type, not 'double'}}
@@ -102,7 +102,7 @@
   foo();
 
 #pragma omp target
-#pragma omp teams thread_limit (-10u)
+#pragma omp teams thread_limit (-10u) // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
   foo();
 
 #pragma omp target
Index: test/Sema/unary-minus-unsigned.c
===================================================================
--- test/Sema/unary-minus-unsigned.c
+++ test/Sema/unary-minus-unsigned.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only
+
+void test1(void) {
+  unsigned int a = 1;
+  unsigned long b = 1;
+  unsigned long long c = 1;
+
+  unsigned int a2 = -a;       // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
+  unsigned long b2 = -b;      // expected-warning {{unary minus operator applied to type 'unsigned long', result value is still unsigned}}
+  unsigned long long c2 = -c; // expected-warning {{unary minus operator applied to type 'unsigned long long', result value is still unsigned}}
+
+  int a3 = -a;       // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
+  long b3 = -b;      // expected-warning {{unary minus operator applied to type 'unsigned long', result value is still unsigned}}
+  long long c3 = -c; // expected-warning {{unary minus operator applied to type 'unsigned long long', result value is still unsigned}}
+
+  unsigned int a4 = -1u;         // expected-warning {{unary minus operator applied to type 'unsigned int', result value is still unsigned}}
+  unsigned long b4 = -1ul;       // expected-warning {{unary minus operator applied to type 'unsigned long', result value is still unsigned}}
+  unsigned long long c4 = -1ull; // expected-warning {{unary minus operator applied to type 'unsigned long long', result value is still unsigned}}
+}