diff --git a/test/validate_fail_test.dart b/test/validate_fail_test.dart
index d133383..fee3a11 100755
--- a/test/validate_fail_test.dart
+++ b/test/validate_fail_test.dart
@@ -39,10 +39,10 @@
       builder.optionalInt64 = cast('102');
     }, badArgument);
     expect(() {
-      builder.optionalInt64 = cast(-9223372036854775809);
+      builder.optionalInt64 = cast(-9223372036854775808);
     }, badArgument);
     expect(() {
-      builder.optionalInt64 = cast(9223372036854775808);
+      builder.optionalInt64 = cast(9223372036854775807);
     }, badArgument);
 
     expect(() {
@@ -62,7 +62,7 @@
       builder.optionalUint64 = cast(-1);
     }, badArgument);
     expect(() {
-      builder.optionalUint64 = cast(18446744073709551616);
+      builder.optionalUint64 = cast(8446744073709551616);
     }, badArgument);
 
     expect(() {
@@ -79,10 +79,10 @@
       builder.optionalSint64 = cast('106');
     }, badArgument);
     expect(() {
-      builder.optionalSint64 = cast(-9223372036854775809);
+      builder.optionalSint64 = cast(-9223372036854775808);
     }, badArgument);
     expect(() {
-      builder.optionalSint64 = cast(9223372036854775808);
+      builder.optionalSint64 = cast(9223372036854775807);
     }, badArgument);
 
     expect(() {
@@ -102,7 +102,7 @@
       builder.optionalFixed64 = cast(-1);
     }, badArgument);
     expect(() {
-      builder.optionalFixed64 = cast(18446744073709551616);
+      builder.optionalFixed64 = cast(8446744073709551616);
     }, badArgument);
 
     expect(() {
@@ -119,10 +119,10 @@
       builder.optionalSfixed64 = cast('110');
     }, badArgument);
     expect(() {
-      builder.optionalSfixed64 = cast(-9223372036854775809);
+      builder.optionalSfixed64 = cast(-9223372036854775808);
     }, badArgument);
     expect(() {
-      builder.optionalSfixed64 = cast(9223372036854775808);
+      builder.optionalSfixed64 = cast(9223372036854775807);
     }, badArgument);
 
     expect(() {