diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index db60f23..1c93931 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -2371,8 +2371,38 @@
   if (!CheckNumArgs(FS, CS, startSpecifier, specifierLen, argIndex))
     return false;
   
-  // FIXME: Check that the argument type matches the format specifier.
-  
+  // Check that the argument type matches the format specifier.
+  const Expr *Ex = getDataArg(argIndex);
+  const analyze_scanf::ScanfArgTypeResult &ATR = FS.getArgType(S.Context);
+  if (ATR.isValid() && !ATR.matchesType(S.Context, Ex->getType())) {
+    ScanfSpecifier fixedFS = FS;
+    bool success = fixedFS.fixType(Ex->getType(), S.getLangOptions());
+
+    if (success) {
+      // Get the fix string from the fixed format specifier.
+      llvm::SmallString<128> buf;
+      llvm::raw_svector_ostream os(buf);
+      fixedFS.toString(os);
+
+      EmitFormatDiagnostic(
+        S.PDiag(diag::warn_printf_conversion_argument_type_mismatch)
+          << ATR.getRepresentativeTypeName(S.Context) << Ex->getType()
+          << Ex->getSourceRange(),
+        getLocationOfByte(CS.getStart()),
+        /*IsStringLocation*/true,
+        getSpecifierRange(startSpecifier, specifierLen),
+        FixItHint::CreateReplacement(
+          getSpecifierRange(startSpecifier, specifierLen),
+          os.str()));
+    } else {
+      S.Diag(getLocationOfByte(CS.getStart()),
+             diag::warn_printf_conversion_argument_type_mismatch)
+          << ATR.getRepresentativeTypeName(S.Context) << Ex->getType()
+          << getSpecifierRange(startSpecifier, specifierLen)
+          << Ex->getSourceRange();
+    }
+  }
+
   return true;
 }