diff --git a/src/option.c b/src/option.c
index b6b0bf6..da98071 100644
--- a/src/option.c
+++ b/src/option.c
@@ -8509,11 +8509,6 @@
 	    p_window = Rows - 1;
     }
 
-    if (curbuf->b_p_sts < 0)
-    {
-	errmsg = e_positive;
-	curbuf->b_p_sts = 0;
-    }
     if (curbuf->b_p_ts <= 0)
     {
 	errmsg = e_positive;
@@ -11429,3 +11424,13 @@
 {
     return curbuf->b_p_sw ? curbuf->b_p_sw : curbuf->b_p_ts;
 }
+
+/*
+ * Return the effective softtabstop value for the current buffer, using the
+ * 'tabstop' value when 'softtabstop' is negative.
+ */
+    long
+get_sts_value()
+{
+    return curbuf->b_p_sts < 0 ? get_sw_value() : curbuf->b_p_sts;
+}