diff --git a/README.md b/README.md
index b55c3a92..f9daaa1c 100644
--- a/README.md
+++ b/README.md
@@ -401,6 +401,8 @@ Check the [SUPPORTED_PLATFORMS file](SUPPORTED_PLATFORMS.md).
 
 ### AIX Notes
 
+AIX compilation using IBM XL C/C++ requires version 12.1 or greater.
+
 AIX support for filesystem events requires the non-default IBM `bos.ahafs`
 package to be installed.  This package provides the AIX Event Infrastructure
 that is detected by `autoconf`.
diff --git a/src/unix/atomic-ops.h b/src/unix/atomic-ops.h
index 541a6c86..bc37c0d4 100644
--- a/src/unix/atomic-ops.h
+++ b/src/unix/atomic-ops.h
@@ -36,10 +36,6 @@ UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval)) {
                         : "r" (newval), "0" (oldval)
                         : "memory");
   return out;
-#elif defined(_AIX) && defined(__xlC__)
-  const int out = (*(volatile int*) ptr);
-  __compare_and_swap(ptr, &oldval, newval);
-  return out;
 #elif defined(__MVS__)
   unsigned int op4;
   if (__plo_CSST(ptr, (unsigned int*) &oldval, newval,