diff --git a/clang/lib/Tooling/Inclusions/Stdlib/CSpecialSymbolMap.inc b/clang/lib/Tooling/Inclusions/Stdlib/CSpecialSymbolMap.inc
new file mode 100644
index 0000000000000..a515f69ea6a8c
--- /dev/null
+++ b/clang/lib/Tooling/Inclusions/Stdlib/CSpecialSymbolMap.inc
@@ -0,0 +1,14 @@
+//===-- StdSpecialSymbolMap.inc -----------------------------------*- C -*-===//
+//
+// This is a hand-curated list for C symbols that cannot be parsed/extracted
+// via the include-mapping tool (gen_std.py).
+//
+//===----------------------------------------------------------------------===//
+
+SYMBOL(size_t, None, <stddef.h>)
+SYMBOL(size_t, None, <stdio.h>)
+SYMBOL(size_t, None, <stdlib.h>)
+SYMBOL(size_t, None, <string.h>)
+SYMBOL(size_t, None, <time.h>)
+SYMBOL(size_t, None, <uchar.h>)
+SYMBOL(size_t, None, <wchar.h>)
diff --git a/clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp b/clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp
index adf1b230ff031..0832bcf66145f 100644
--- a/clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp
+++ b/clang/lib/Tooling/Inclusions/Stdlib/StandardLibrary.cpp
@@ -55,11 +55,12 @@ static const SymbolHeaderMapping *getMappingPerLang(Lang L) {
 }
 
 static int countSymbols(Lang Language) {
-  ArrayRef<const char*> Symbols;
+  ArrayRef<const char *> Symbols;
 #define SYMBOL(Name, NS, Header) #NS #Name,
   switch (Language) {
   case Lang::C: {
     static constexpr const char *CSymbols[] = {
+#include "CSpecialSymbolMap.inc"
 #include "CSymbolMap.inc"
     };
     Symbols = CSymbols;
@@ -147,6 +148,7 @@ static int initialize(Lang Language) {
   switch (Language) {
   case Lang::C: {
     static constexpr Symbol CSymbols[] = {
+#include "CSpecialSymbolMap.inc"
 #include "CSymbolMap.inc"
     };
     for (const Symbol &S : CSymbols)
diff --git a/clang/unittests/Tooling/StandardLibraryTest.cpp b/clang/unittests/Tooling/StandardLibraryTest.cpp
index edca31649accf..e4c109f3d580d 100644
--- a/clang/unittests/Tooling/StandardLibraryTest.cpp
+++ b/clang/unittests/Tooling/StandardLibraryTest.cpp
@@ -185,6 +185,19 @@ TEST(StdlibTest, RecognizerForC99) {
             stdlib::Symbol::named("", "uint8_t", stdlib::Lang::C));
 }
 
+TEST(StdlibTest, SpecialCMappings) {
+  TestInputs Input("typedef char size_t;");
+  Input.Language = TestLanguage::Lang_C99;
+  TestAST AST(Input);
+
+  auto &SizeT = lookup(AST, "size_t");
+  stdlib::Recognizer Recognizer;
+  auto ActualSym = Recognizer(&SizeT);
+  assert(ActualSym);
+  EXPECT_EQ(ActualSym, stdlib::Symbol::named("", "size_t", stdlib::Lang::C));
+  EXPECT_EQ(ActualSym->header()->name(), "<stddef.h>");
+}
+
 } // namespace
 } // namespace tooling
 } // namespace clang