Index: b/Modules/CMakeCCompilerId.c.in
===================================================================
--- a/Modules/CMakeCCompilerId.c.in
+++ b/Modules/CMakeCCompilerId.c.in
@@ -40,6 +40,8 @@ char const *info_cray = "INFO" ":" "comp
 # else
 #  define C_DIALECT
 # endif
+#elif __STDC_VERSION__ >= 201710L
+# define C_DIALECT "17"
 #elif __STDC_VERSION__ >= 201000L
 # define C_DIALECT "11"
 #elif __STDC_VERSION__ >= 199901L
Index: b/Modules/Compiler/GNU-C.cmake
===================================================================
--- a/Modules/Compiler/GNU-C.cmake
+++ b/Modules/Compiler/GNU-C.cmake
@@ -22,4 +22,4 @@ elseif (NOT CMAKE_C_COMPILER_VERSION VER
   set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu1x")
 endif()
 
-__compiler_check_default_language_standard(C 3.4 90 5.0 11)
+__compiler_check_default_language_standard(C 3.4 90 5.0 11 8.0 17)
Index: b/Source/cmLocalGenerator.cxx
===================================================================
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1566,6 +1566,7 @@ void cmLocalGenerator::AddCompilerRequir
     langStdMap["CXX"].push_back("11");
     langStdMap["CXX"].push_back("98");
 
+    langStdMap["C"].push_back("17");
     langStdMap["C"].push_back("11");
     langStdMap["C"].push_back("99");
     langStdMap["C"].push_back("90");
Index: b/Source/cmMakefile.cxx
===================================================================
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -4161,7 +4161,7 @@ static const char* const CXX_FEATURES[]
   FEATURE_STRING) };
 #undef FEATURE_STRING
 
-static const char* const C_STANDARDS[] = { "90", "99", "11" };
+static const char* const C_STANDARDS[] = { "90", "99", "11", "17" };
 static const char* const CXX_STANDARDS[] = { "98", "11", "14", "17" };
 
 bool cmMakefile::AddRequiredTargetFeature(cmTarget* target,
Index: b/Tests/CompileFeatures/CMakeLists.txt
===================================================================
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -214,6 +214,7 @@ if (C_expected_features)
     if (std_flag_idx EQUAL -1)
       add_executable(default_dialect_C default_dialect.c)
       target_compile_definitions(default_dialect_C PRIVATE
+        DEFAULT_C17=$<EQUAL:${CMAKE_C_STANDARD_DEFAULT},17>
         DEFAULT_C11=$<EQUAL:${CMAKE_C_STANDARD_DEFAULT},11>
         DEFAULT_C99=$<EQUAL:${CMAKE_C_STANDARD_DEFAULT},99>
         DEFAULT_C90=$<EQUAL:${CMAKE_C_STANDARD_DEFAULT},90>
Index: b/Tests/CompileFeatures/default_dialect.c
===================================================================
--- a/Tests/CompileFeatures/default_dialect.c
+++ b/Tests/CompileFeatures/default_dialect.c
@@ -1,5 +1,9 @@
 
-#if DEFAULT_C11
+#if DEFAULT_C17
+#if __STDC_VERSION__ < 201710L
+#error Unexpected value for __STDC_VERSION__.
+#endif
+#elif DEFAULT_C11
 #if __STDC_VERSION__ < 201112L
 #error Unexpected value for __STDC_VERSION__.
 #endif