Index: clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
+++ clang-tools-extra/clang-tidy/cppcoreguidelines/InitVariablesCheck.cpp
@@ -60,6 +60,8 @@
   const ASTContext &Context = *Result.Context;
   const SourceManager &Source = Context.getSourceManager();
 
+  if (MatchedDecl->isInvalidDecl())
+    return;
   // We want to warn about cases where the type name
   // comes from a macro like this:
   //
Index: clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/init-variables-clang-diagnostic-error.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/init-variables-clang-diagnostic-error.cpp
@@ -0,0 +1,17 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-init-variables %t -fix-errors --
+
+#include "unknown.h"
+// CHECK-MESSAGES: :[[@LINE-1]]:10: error: 'unknown.h' file not found [clang-diagnostic-error]
+
+namespace std {
+template <typename T>
+struct vector {
+  vector();
+};
+
+void test() {
+  int a;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: variable 'a' is not initialized [cppcoreguidelines-init-variables]
+  // CHECK-FIXES: {{^}}  int a = 0;{{$}}
+  std::vector<int> arr;
+}