diff --git a/src/extent.c b/src/extent.c
index ee50aff8..7e10b7f5 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -988,9 +988,12 @@ extent_recycle_split(tsdn_t *tsdn, arena_t *arena,
 			extent_deregister(tsdn, to_salvage);
 		}
 		if (to_leak != NULL) {
+			void *leak = extent_base_get(to_leak);
 			extent_deregister(tsdn, to_leak);
 			extents_leak(tsdn, arena, r_extent_hooks, extents,
 			    to_leak, growing_retained);
+			assert(extent_lock_from_addr(tsdn, rtree_ctx, leak)
+			    == NULL);
 		}
 		return NULL;
 	}
diff --git a/test/include/test/extent_hooks.h b/test/include/test/extent_hooks.h
index ea012857..1f062015 100644
--- a/test/include/test/extent_hooks.h
+++ b/test/include/test/extent_hooks.h
@@ -266,6 +266,8 @@ extent_merge_hook(extent_hooks_t *extent_hooks, void *addr_a, size_t size_a,
 	    "extent_hooks should be same as pointer used to set hooks");
 	assert_ptr_eq(extent_hooks->merge, extent_merge_hook,
 	    "Wrong hook function");
+	assert_ptr_eq((void *)((uintptr_t)addr_a + size_a), addr_b,
+	    "Extents not mergeable");
 	called_merge = true;
 	if (!try_merge) {
 		return true;
diff --git a/test/integration/extent.c b/test/integration/extent.c
index 1dcf2176..7100b6af 100644
--- a/test/integration/extent.c
+++ b/test/integration/extent.c
@@ -98,7 +98,8 @@ test_extent_body(unsigned arena_ind) {
 	dallocx(p, flags);
 }
 
-TEST_BEGIN(test_extent_manual_hook) {
+static void
+test_manual_hook_body(void) {
 	unsigned arena_ind;
 	size_t old_size, new_size, sz;
 	size_t hooks_mib[3];
@@ -139,8 +140,9 @@ TEST_BEGIN(test_extent_manual_hook) {
 	assert_ptr_ne(old_hooks->merge, extent_merge_hook,
 	    "Unexpected extent_hooks error");
 
-	test_skip_if(check_background_thread_enabled());
-	test_extent_body(arena_ind);
+	if (check_background_thread_enabled()) {
+		test_extent_body(arena_ind);
+	}
 
 	/* Restore extent hooks. */
 	assert_d_eq(mallctlbymib(hooks_mib, hooks_miblen, NULL, NULL,
@@ -165,6 +167,21 @@ TEST_BEGIN(test_extent_manual_hook) {
 	assert_ptr_eq(old_hooks->merge, default_hooks->merge,
 	    "Unexpected extent_hooks error");
 }
+
+TEST_BEGIN(test_extent_manual_hook) {
+	test_manual_hook_body();
+
+	/* Test failure paths. */
+	try_split = false;
+	test_manual_hook_body();
+	try_merge = false;
+	test_manual_hook_body();
+	try_purge_lazy = false;
+	try_purge_forced = false;
+	test_manual_hook_body();
+
+	try_split = try_merge = try_purge_lazy = try_purge_forced = true;
+}
 TEST_END
 
 TEST_BEGIN(test_extent_auto_hook) {