diff --git a/lib/checkio.cpp b/lib/checkio.cpp
index c8c0e52d2..4bdd10c91 100644
--- a/lib/checkio.cpp
+++ b/lib/checkio.cpp
@@ -905,6 +905,9 @@ void CheckIO::checkWrongPrintfScanfArguments()
                                                 case 'L':
                                                     if (argInfo.typeToken->str() != "long" || !argInfo.typeToken->isLong())
                                                         invalidScanfArgTypeError_int(tok, numFormat, specifier, &argInfo, true);
+                                                    else if (argInfo.typeToken->originalName() == "size_t" ||
+                                                             argInfo.typeToken->originalName() == "uintmax_t")
+                                                        invalidScanfArgTypeError_int(tok, numFormat, specifier, &argInfo, true);
                                                     break;
                                                 default:
                                                     if (argInfo.typeToken->str() != "int")
diff --git a/test/testio.cpp b/test/testio.cpp
index 66ecabebb..2d4ac7522 100644
--- a/test/testio.cpp
+++ b/test/testio.cpp
@@ -1163,7 +1163,7 @@ private:
             check(code, true, false, Settings::Win32A);
             ASSERT_EQUALS(result, errout.str());
             check(code, true, false, Settings::Win64);
-            // FIXME ASSERT_EQUALS(result_win64, errout.str());
+            ASSERT_EQUALS(result_win64, errout.str());
         }
 
         {