--- a/src/include/port/atomics/arch-ppc.h
+++ b/src/include/port/atomics/arch-ppc.h
@@ -96,3 +96,4 @@ pg_atomic_compare_exchange_u32_impl(volatile pg_atomic_uint32 *ptr,
 	if (__builtin_constant_p(*expected) &&
-		*expected <= PG_INT16_MAX && *expected >= PG_INT16_MIN)
+		(int32) *expected <= PG_INT16_MAX &&
+		(int32) *expected >= PG_INT16_MIN)
 		__asm__ __volatile__(
@@ -185,3 +186,4 @@ pg_atomic_compare_exchange_u64_impl(volatile pg_atomic_uint64 *ptr,
 	if (__builtin_constant_p(*expected) &&
-		*expected <= PG_INT16_MAX && *expected >= PG_INT16_MIN)
+		(int64) *expected <= PG_INT16_MAX &&
+		(int64) *expected >= PG_INT16_MIN)
 		__asm__ __volatile__(