diff --git a/doc/variables.xml b/doc/variables.xml
index c7ac6ffe..96b8b4e6 100644
--- a/doc/variables.xml
+++ b/doc/variables.xml
@@ -675,8 +675,8 @@
         </term>
         <listitem>
             Download data from URI using Curl at the
-            specified interval. The interval may be a floating
-            point value greater than 0, otherwise defaults to 15
+            specified interval. The interval may be a positive floating
+            point value (0 is allowed), otherwise defaults to 15
             minutes. Most useful when used in conjunction with Lua
             and the Lua API. This object is threaded, and once a
             thread is created it can't be explicitly destroyed.
diff --git a/src/ccurl_thread.cc b/src/ccurl_thread.cc
index 82401dde..fdd0f14b 100644
--- a/src/ccurl_thread.cc
+++ b/src/ccurl_thread.cc
@@ -222,7 +222,7 @@ void curl_parse_arg(struct text_object *obj, const char *arg)
 		NORM_ERR("wrong number of arguments for $curl");
 		return;
 	}
-	cd->interval = interval > 0 ? interval * 60 : 15*60;
+	cd->interval = (argc == 2 && interval >= 0) ? interval * 60 : 15*60;
 	obj->data.opaque = cd;
 }