diff --git a/src/ctl.c b/src/ctl.c
index a193605d..fa52a6cc 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -1327,45 +1327,51 @@ static int
 arena_i_dss_ctl(const size_t *mib, size_t miblen, void *oldp, size_t *oldlenp,
     void *newp, size_t newlen)
 {
-	int ret, i;
-	bool match, err;
-	const char *dss;
+	int ret;
+	const char *dss = NULL;
 	unsigned arena_ind = mib[1];
 	dss_prec_t dss_prec_old = dss_prec_limit;
 	dss_prec_t dss_prec = dss_prec_limit;
 
 	malloc_mutex_lock(&ctl_mtx);
 	WRITE(dss, const char *);
-	match = false;
-	for (i = 0; i < dss_prec_limit; i++) {
-		if (strcmp(dss_prec_names[i], dss) == 0) {
-			dss_prec = i;
-			match = true;
-			break;
+	if (dss != NULL) {
+		int i;
+		bool match = false;
+
+		for (i = 0; i < dss_prec_limit; i++) {
+			if (strcmp(dss_prec_names[i], dss) == 0) {
+				dss_prec = i;
+				match = true;
+				break;
+			}
+		}
+
+		if (match == false) {
+			ret = EINVAL;
+			goto label_return;
 		}
-	}
-	if (match == false) {
-		ret = EINVAL;
-		goto label_return;
 	}
 
 	if (arena_ind < ctl_stats.narenas) {
 		arena_t *arena = arenas[arena_ind];
-		if (arena != NULL) {
-			dss_prec_old = arena_dss_prec_get(arena);
-			err = arena_dss_prec_set(arena, dss_prec);
-		} else
-			err = true;
+		if (arena == NULL || (dss_prec != dss_prec_limit &&
+		    arena_dss_prec_set(arena, dss_prec))) {
+			ret = EFAULT;
+			goto label_return;
+		}
+		dss_prec_old = arena_dss_prec_get(arena);
 	} else {
+		if (dss_prec != dss_prec_limit &&
+		    chunk_dss_prec_set(dss_prec)) {
+			ret = EFAULT;
+			goto label_return;
+		}
 		dss_prec_old = chunk_dss_prec_get();
-		err = chunk_dss_prec_set(dss_prec);
 	}
+
 	dss = dss_prec_names[dss_prec_old];
 	READ(dss, const char *);
-	if (err) {
-		ret = EFAULT;
-		goto label_return;
-	}
 
 	ret = 0;
 label_return:
diff --git a/test/unit/mallctl.c b/test/unit/mallctl.c
index 7a8b55f5..c70473cc 100644
--- a/test/unit/mallctl.c
+++ b/test/unit/mallctl.c
@@ -268,12 +268,25 @@ TEST_BEGIN(test_arena_i_dss)
 	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_new, &sz, &dss_prec_old,
 	    sizeof(dss_prec_old)), 0, "Unexpected mallctl() failure");
 
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_old, &sz, NULL, 0), 0,
+	    "Unexpected mallctl() failure");
+	assert_str_ne(dss_prec_old, "primary",
+	    "Unexpected value for dss precedence");
+
 	mib[1] = narenas_total_get();
 	dss_prec_new = "disabled";
 	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_old, &sz, &dss_prec_new,
 	    sizeof(dss_prec_new)), 0, "Unexpected mallctl() failure");
 	assert_str_ne(dss_prec_old, "primary",
 	    "Unexpected default for dss precedence");
+
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_new, &sz, &dss_prec_old,
+	    sizeof(dss_prec_new)), 0, "Unexpected mallctl() failure");
+
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_old, &sz, NULL, 0), 0,
+	    "Unexpected mallctl() failure");
+	assert_str_ne(dss_prec_old, "primary",
+	    "Unexpected value for dss precedence");
 }
 TEST_END