diff --git a/test/unit/from_current_z.cpp b/test/unit/from_current_z.cpp
index 52bacb34..95462ac0 100644
--- a/test/unit/from_current_z.cpp
+++ b/test/unit/from_current_z.cpp
@@ -16,16 +16,22 @@ using namespace std::literals;
 // NOTE: returning something and then return stacktrace_from_current_3(line_numbers) * 2; later helps prevent the call from
 // being optimized to a jmp
 CPPTRACE_FORCE_NO_INLINE int stacktrace_from_current_z_3(std::vector<int>& line_numbers) {
+    // just here to differentiate from the non-z version to prevent ICF if LTO is being used
+    [[maybe_unused]] volatile int x = 1;
     line_numbers.insert(line_numbers.begin(), __LINE__ + 1);
     throw std::runtime_error("foobar");
 }
 
 CPPTRACE_FORCE_NO_INLINE int stacktrace_from_current_z_2(std::vector<int>& line_numbers) {
+    // just here to differentiate from the non-z version to prevent ICF if LTO is being used
+    [[maybe_unused]] volatile int x = 1;
     line_numbers.insert(line_numbers.begin(), __LINE__ + 1);
     return stacktrace_from_current_z_3(line_numbers) * 2;
 }
 
 CPPTRACE_FORCE_NO_INLINE int stacktrace_from_current_z_1(std::vector<int>& line_numbers) {
+    // just here to differentiate from the non-z version to prevent ICF if LTO is being used
+    [[maybe_unused]] volatile int x = 1;
     line_numbers.insert(line_numbers.begin(), __LINE__ + 1);
     return stacktrace_from_current_z_2(line_numbers) * 2;
 }