diff --git a/sys/cddl/compat/opensolaris/sys/atomic.h b/sys/cddl/compat/opensolaris/sys/atomic.h
--- a/sys/cddl/compat/opensolaris/sys/atomic.h
+++ b/sys/cddl/compat/opensolaris/sys/atomic.h
@@ -157,7 +157,7 @@
 	return (atomic_add_64_nv(target, -1));
 }
 
-#if !defined(COMPAT_32BIT) && defined(__LP64__)
+#ifdef __LP64__
 static __inline void *
 atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 {
@@ -171,6 +171,6 @@
 	return ((void *)atomic_cas_32((volatile uint32_t *)target,
 	    (uint32_t)cmp, (uint32_t)newval));
 }
-#endif	/* !defined(COMPAT_32BIT) && defined(__LP64__) */
+#endif	/* __LP64__ */
 
 #endif	/* !_OPENSOLARIS_SYS_ATOMIC_H_ */
diff --git a/sys/contrib/openzfs/include/os/freebsd/spl/sys/atomic.h b/sys/contrib/openzfs/include/os/freebsd/spl/sys/atomic.h
--- a/sys/contrib/openzfs/include/os/freebsd/spl/sys/atomic.h
+++ b/sys/contrib/openzfs/include/os/freebsd/spl/sys/atomic.h
@@ -167,7 +167,7 @@
 	return (atomic_add_64_nv(target, -1));
 }
 
-#if !defined(COMPAT_32BIT) && defined(__LP64__)
+#ifdef __LP64__
 static __inline void *
 atomic_cas_ptr(volatile void *target, void *cmp,  void *newval)
 {
@@ -181,7 +181,7 @@
 	return ((void *)atomic_cas_32((volatile uint32_t *)target,
 	    (uint32_t)cmp, (uint32_t)newval));
 }
-#endif	/* !defined(COMPAT_32BIT) && defined(__LP64__) */
+#endif	/* __LP64__ */
 
 #else /* _STANDALONE */
 /*