diff --git a/include/gcc/ppc/ck_pr.h b/include/gcc/ppc/ck_pr.h
index ef9105c..5fe0c95 100644
--- a/include/gcc/ppc/ck_pr.h
+++ b/include/gcc/ppc/ck_pr.h
@@ -79,7 +79,7 @@ CK_PR_FENCE(load_store, "lwsync")
 CK_PR_FENCE(memory, "sync")
 CK_PR_FENCE(acquire, "lwsync")
 CK_PR_FENCE(release, "lwsync")
-CK_PR_FENCE(lock, "isync")
+CK_PR_FENCE(lock, "lwsync")
 CK_PR_FENCE(unlock, "lwsync")
 
 #undef CK_PR_FENCE
diff --git a/include/gcc/ppc64/ck_pr.h b/include/gcc/ppc64/ck_pr.h
index 966cac2..5abd05c 100644
--- a/include/gcc/ppc64/ck_pr.h
+++ b/include/gcc/ppc64/ck_pr.h
@@ -82,7 +82,7 @@ CK_PR_FENCE(load_store, "lwsync")
 CK_PR_FENCE(memory, "sync")
 CK_PR_FENCE(acquire, "lwsync")
 CK_PR_FENCE(release, "lwsync")
-CK_PR_FENCE(lock, "isync")
+CK_PR_FENCE(lock, "lwsync")
 CK_PR_FENCE(unlock, "lwsync")
 
 #undef CK_PR_FENCE