diff --git a/fibb_tsc/timestamp32.s b/fibb_tsc/timestamp32.s
index ba269a7..d24c06e 100644
--- a/fibb_tsc/timestamp32.s
+++ b/fibb_tsc/timestamp32.s
@@ -6,8 +6,11 @@
 .text
 
 timestamp:
+push %ebx
+
 xor %eax, %eax
 cpuid
 rdtsc
 
+pop %ebx
 ret
diff --git a/fibb_tsc/timestamp64.s b/fibb_tsc/timestamp64.s
index b7705ff..48d64c2 100644
--- a/fibb_tsc/timestamp64.s
+++ b/fibb_tsc/timestamp64.s
@@ -6,6 +6,8 @@
 .text
 
 timestamp:
+push %rbx
+
 xor %rax, %rax
 cpuid
 rdtsc
@@ -13,4 +15,5 @@ rdtsc
 shl $32, %rdx
 or %rdx, %rax
 
+pop %rbx
 ret