diff --git a/src/option.c b/src/option.c
index 717812c..1b581ed 100644
--- a/src/option.c
+++ b/src/option.c
@@ -1990,6 +1990,8 @@
 
     // Set the new value.
     *(char_u **)(varp) = newval;
+    if (newval == NULL)
+	*(char_u **)(varp) = empty_option;
 
 #if defined(FEAT_EVAL)
     if (!starting