diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.h
@@ -22,6 +22,8 @@
 /// The check supports these options:
 ///   - `UseHeaderFileExtension`: Whether to use file extension to distinguish
 ///     header files. True by default.
+///   - `CheckCCode`: Adds C99 to the minimum Language Requirements for this
+///     Checker. Disabled by default because this Checker wasn't build for C.
 ///   - `HeaderFileExtensions`: a semicolon-separated list of filename
 ///     extensions of header files (The filename extension should not contain
 ///     "." prefix). ";h;hh;hpp;hxx" by default.
@@ -35,6 +37,9 @@
 public:
   DefinitionsInHeadersCheck(StringRef Name, ClangTidyContext *Context);
   bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    if (CheckCCode) {
+      return LangOpts.CPlusPlus11 || LangOpts.C99;
+    }
     return LangOpts.CPlusPlus11;
   }
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
@@ -43,6 +48,7 @@
 
 private:
   const bool UseHeaderFileExtension;
+  const bool CheckCCode;
   const std::string RawStringHeaderFileExtensions;
   utils::FileExtensionsSet HeaderFileExtensions;
 };
diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
--- a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
@@ -31,6 +31,7 @@
                                                      ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
       UseHeaderFileExtension(Options.get("UseHeaderFileExtension", true)),
+      CheckCCode(Options.get("CheckCCode", false)),
       RawStringHeaderFileExtensions(Options.getLocalOrGlobal(
           "HeaderFileExtensions", utils::defaultHeaderFileExtensions())) {
   if (!utils::parseFileExtensions(RawStringHeaderFileExtensions,
@@ -44,6 +45,7 @@
 void DefinitionsInHeadersCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "UseHeaderFileExtension", UseHeaderFileExtension);
+  Options.store(Opts, "CheckCCode", CheckCCode);
   Options.store(Opts, "HeaderFileExtensions", RawStringHeaderFileExtensions);
 }
 
diff --git a/clang-tools-extra/docs/clang-tidy/checks/misc-definitions-in-headers.rst b/clang-tools-extra/docs/clang-tidy/checks/misc-definitions-in-headers.rst
--- a/clang-tools-extra/docs/clang-tidy/checks/misc-definitions-in-headers.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/misc-definitions-in-headers.rst
@@ -102,3 +102,8 @@
 
    When `true`, the check will use the file extension to distinguish header
    files. Default is `true`.
+
+.. option:: CheckCCode
+
+   When `true` C99 is added to the minimum language requirements for this 
+   Cecker. Default is `false` because this Checker was not build for C.