diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5953,7 +5953,7 @@
   "excess elements in char array initializer">,
   InGroup<ExcessInitializers>;
 def err_initializer_string_for_char_array_too_long : Error<
-  "initializer-string for char array is too long">;
+  "initializer-string for char array is too long, array size is %0 but initializer has size %1 (including the null terminating character)">;
 def ext_initializer_string_for_char_array_too_long : ExtWarn<
   "initializer-string for char array is too long">,
   InGroup<ExcessInitializers>;
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -239,6 +239,8 @@
     if (StrLength > CAT->getSize().getZExtValue())
       S.Diag(Str->getBeginLoc(),
              diag::err_initializer_string_for_char_array_too_long)
+          << CAT->getSize().getZExtValue()
+          << StrLength
           << Str->getSourceRange();
   } else {
     // C99 6.7.8p14.
diff --git a/clang/test/CXX/dcl.decl/dcl.init/dcl.init.string/p2.cpp b/clang/test/CXX/dcl.decl/dcl.init/dcl.init.string/p2.cpp
--- a/clang/test/CXX/dcl.decl/dcl.init/dcl.init.string/p2.cpp
+++ b/clang/test/CXX/dcl.decl/dcl.init/dcl.init.string/p2.cpp
@@ -1,2 +1,3 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
-char test1[1]="f"; // expected-error {{initializer-string for char array is too long}}
+char test1[1]="f"; // expected-error {{initializer-string for char array is too long, array size is 1 but initializer has size 2 (including the null terminating character)}}
+char test2[1]="";