diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
index d455473673b09f..1660d976ff0be3 100644
--- a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -403,6 +403,8 @@ void ClangTidyDiagnosticConsumer::HandleDiagnostic(
 
     bool IsWarningAsError = DiagLevel == DiagnosticsEngine::Warning &&
                             Context.treatAsError(CheckName);
+    if (IsWarningAsError)
+      Level = ClangTidyError::Error;
     Errors.emplace_back(CheckName, Level, Context.getCurrentBuildDirectory(),
                         IsWarningAsError);
   }
diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/export-diagnostics.cpp b/clang-tools-extra/test/clang-tidy/infrastructure/export-diagnostics.cpp
index 16ad4f175cab94..ca2184332f9a45 100644
--- a/clang-tools-extra/test/clang-tidy/infrastructure/export-diagnostics.cpp
+++ b/clang-tools-extra/test/clang-tidy/infrastructure/export-diagnostics.cpp
@@ -1,5 +1,5 @@
 // RUN: grep -Ev "// *[A-Z-]+:" %s > %t-input.cpp
-// RUN: not clang-tidy %t-input.cpp -checks='-*,google-explicit-constructor,clang-diagnostic-missing-prototypes,clang-diagnostic-zero-length-array' -export-fixes=%t.yaml -- -Wmissing-prototypes -Wzero-length-array > %t.msg 2>&1
+// RUN: not clang-tidy %t-input.cpp -checks='-*,google-explicit-constructor,clang-diagnostic-missing-prototypes,clang-diagnostic-zero-length-array' --warnings-as-errors='clang-diagnostic-missing-prototypes,google-explicit-constructor' -export-fixes=%t.yaml -- -Wmissing-prototypes -Wzero-length-array > %t.msg 2>&1
 // RUN: FileCheck -input-file=%t.msg -check-prefix=CHECK-MESSAGES %s -implicit-check-not='{{warning|error|note}}:'
 // RUN: FileCheck -input-file=%t.yaml -check-prefix=CHECK-YAML %s
 #define X(n) void n ## n() {}
@@ -10,9 +10,10 @@ int b[0];
 void test(x);
 struct Foo {
   member;
+  Foo(int) {}
 };
 
-// CHECK-MESSAGES: -input.cpp:2:1: warning: no previous prototype for function 'ff' [clang-diagnostic-missing-prototypes]
+// CHECK-MESSAGES: -input.cpp:2:1: error: no previous prototype for function 'ff' [clang-diagnostic-missing-prototypes,-warnings-as-errors]
 // CHECK-MESSAGES: -input.cpp:1:19: note: expanded from macro 'X'
 // CHECK-MESSAGES: {{^}}note: expanded from here{{$}}
 // CHECK-MESSAGES: -input.cpp:2:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
@@ -21,6 +22,7 @@ struct Foo {
 // CHECK-MESSAGES: -input.cpp:4:7: warning: zero size arrays are an extension [clang-diagnostic-zero-length-array]
 // CHECK-MESSAGES: -input.cpp:6:11: error: unknown type name 'x' [clang-diagnostic-error]
 // CHECK-MESSAGES: -input.cpp:8:3: error: a type specifier is required for all declarations [clang-diagnostic-error]
+// CHECK-MESSAGES: -input.cpp:9:3: error: single-argument constructors must be marked explicit to avoid unintentional implicit conversions [google-explicit-constructor,-warnings-as-errors]
 
 // CHECK-YAML: ---
 // CHECK-YAML-NEXT: MainSourceFile:  '{{.*}}-input.cpp'
@@ -52,7 +54,7 @@ struct Foo {
 // CHECK-YAML-NEXT:         FilePath:        '{{.*}}-input.cpp'
 // CHECK-YAML-NEXT:         FileOffset:      13
 // CHECK-YAML-NEXT:         Replacements:    []
-// CHECK-YAML-NEXT:     Level:           Warning
+// CHECK-YAML-NEXT:     Level:           Error
 // CHECK-YAML-NEXT:     BuildDirectory:  '{{.*}}'
 // CHECK-YAML-NEXT:   - DiagnosticName:  clang-diagnostic-error
 // CHECK-YAML-NEXT:     DiagnosticMessage:
@@ -94,4 +96,16 @@ struct Foo {
 // CHECK-YAML-NEXT:       Replacements:    []
 // CHECK-YAML-NEXT:     Level:           Error
 // CHECK-YAML-NEXT:     BuildDirectory:  '{{.*}}'
+// CHECK-YAML-NEXT:   - DiagnosticName:  google-explicit-constructor
+// CHECK-YAML-NEXT:     DiagnosticMessage:
+// CHECK-YAML-NEXT:       Message:         single-argument constructors must be marked explicit to avoid unintentional implicit conversions
+// CHECK-YAML-NEXT:       FilePath:        '{{.*}}-input.cpp'
+// CHECK-YAML-NEXT:       FileOffset:      96
+// CHECK-YAML-NEXT:       Replacements:
+// CHECK-YAML-NEXT:         - FilePath:        '{{.*}}-input.cpp'
+// CHECK-YAML-NEXT:           Offset:          96
+// CHECK-YAML-NEXT:           Length:          0
+// CHECK-YAML-NEXT:           ReplacementText: 'explicit '
+// CHECK-YAML-NEXT:     Level:           Error
+// CHECK-YAML-NEXT:     BuildDirectory:  '{{.*}}'
 // CHECK-YAML-NEXT: ...