diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2522cae0c31..d6c16bce31e 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -411,6 +411,11 @@ typedef unsigned int slock_t;
  * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  * But if the spinlock is in ordinary memory, we can use lwsync instead for
  * better performance.
+ *
+ * Ordinarily, we'd code the branches here using GNU-style local symbols, that
+ * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
+ * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
+ * Instead, use %= to make the symbols unique.
  */
 static __inline__ int
 tas(volatile slock_t *lock)
@@ -421,17 +426,17 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     TAS_fail%=	\n"
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     TAS_ok%=	\n"
+"TAS_fail%=: \n"
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       TAS_out%=	\n"
+"TAS_ok%=: \n"
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+"TAS_out%=: \n"
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");