diff --git a/sandboxed_api/examples/stringop/lib/stringop.cc b/sandboxed_api/examples/stringop/lib/stringop.cc
index 805f3f3..decac6e 100644
--- a/sandboxed_api/examples/stringop/lib/stringop.cc
+++ b/sandboxed_api/examples/stringop/lib/stringop.cc
@@ -79,17 +79,20 @@ extern "C" const void* get_raw_c_string() { return "Ten chars."; }
 
 extern "C" void nop() {}
 
-// The "no tail-call" annotation and the additional indirection ensure that this
-// function shows up in the violation stack trace. Otherwise, depending on
-// optimization level and optimizer aggressiveness, functions may be inlined,
-// hoisted or omitted (in case of tail calls).
+// The "no tail-call" annotation and the additional indirection ensure that
+// either this function or its calling function shows up in the violation stack
+// trace. Otherwise, depending on optimization level and optimizer
+// aggressiveness, functions may be inlined, hoisted or omitted (in case of tail
+// calls).
 static ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL void
 ViolateIndirect() {
   ptrace((__ptrace_request)990, 991, 992, 993);
-  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
 }
 
-extern "C" void violate() {
+// Using block syntax here, because SAPI's libclang based header generator won't
+// parse the attribute annotations otherwise.
+extern "C" {
+ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL void violate() {
   ViolateIndirect();
-  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
 }
diff --git a/sandboxed_api/sapi_test.cc b/sandboxed_api/sapi_test.cc
index d2bade6..d440c7b 100644
--- a/sandboxed_api/sapi_test.cc
+++ b/sandboxed_api/sapi_test.cc
@@ -143,7 +143,15 @@ TEST(SapiTest, HasStackTraces) {
   StringopApi api(sandbox.get());
   EXPECT_THAT(api.violate(), StatusIs(absl::StatusCode::kUnavailable));
   const auto& result = sandbox->AwaitResult();
-  EXPECT_THAT(result.GetStackTrace(), HasSubstr("ViolateIndirect"));
+  EXPECT_THAT(
+      result.GetStackTrace(),
+      // Check that at least one expected function is present in the stack
+      // trace.
+      // Note: Typically, in optimized builds, on x86-64, only
+      // "ViolateIndirect()" will be present in the stack trace. On POWER, all
+      // stack frames are generated, but libunwind will be unable to track
+      // "ViolateIndirect()" on the stack and instead show its IP as zero.
+      AnyOf(HasSubstr("ViolateIndirect"), HasSubstr("violate")));
   EXPECT_THAT(result.final_status(), Eq(sandbox2::Result::VIOLATION));
 }