diff --git a/test/behavior/bugs/12776.zig b/test/behavior/bugs/12776.zig
index 2061d6e8041803031e86bfe886a1d2402f8212a2..91df319decabc45890688b2af83f8c3c3fae2764 100644
--- a/test/behavior/bugs/12776.zig
+++ b/test/behavior/bugs/12776.zig
@@ -29,6 +29,7 @@ const CPU = packed struct {
 };
 
 test {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
diff --git a/test/behavior/bugs/13664.zig b/test/behavior/bugs/13664.zig
index 828408510ddcfe2aaa1217b85662a5aa0681f2ed..02b719cfba42fd91979301d755644fe329899fc3 100644
--- a/test/behavior/bugs/13664.zig
+++ b/test/behavior/bugs/13664.zig
@@ -17,6 +17,7 @@ test {
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
 
     const timestamp: i64 = value();
     const id = ID{ .fields = Fields{