diff --git a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
--- a/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp
@@ -54,6 +54,7 @@
   std::replace(Guard.begin(), Guard.end(), '/', '_');
   std::replace(Guard.begin(), Guard.end(), '.', '_');
   std::replace(Guard.begin(), Guard.end(), '-', '_');
+  std::replace(Guard.begin(), Guard.end(), ':', '_');
 
   // The prevalent style in clang is LLVM_CLANG_FOO_BAR_H
   if (StringRef(Guard).startswith("clang"))
diff --git a/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp b/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
--- a/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp
@@ -267,6 +267,15 @@
             runHeaderGuardCheck(
                 "", "\\\\?\\C:\\llvm-project\\clang-tools-extra\\clangd\\foo.h",
                 StringRef("header is missing header guard")));
+
+  EXPECT_EQ("#ifndef C__TEST_FOO_H\n"
+            "#define C__TEST_FOO_H\n"
+            "\n"
+            "\n"
+            "#endif\n",
+            runHeaderGuardCheck("", "c:\\test\\foo.h",
+                                StringRef("header is missing header guard")));
+
 #endif
 }