diff --git a/src/ALabel.cpp b/src/ALabel.cpp
index 7f9143b3..4e6d3349 100644
--- a/src/ALabel.cpp
+++ b/src/ALabel.cpp
@@ -17,12 +17,17 @@ ALabel::ALabel(const Json::Value& config, const std::string& name, const std::st
               config["format-alt"].isString() || config["menu"].isString() || enable_click,
               enable_scroll),
       format_(config_["format"].isString() ? config_["format"].asString() : format),
+
+      // Leave the default option outside of the std::max(1L, ...), because the zero value
+      // (default) is used in modules/custom.cpp to make the difference between
+      // two types of custom scripts. Fixes #4521.
       interval_(config_["interval"] == "once"
                     ? std::chrono::milliseconds::max()
                     : std::chrono::milliseconds(
-                          std::max(1L, // Minimum 1ms due to millisecond precision
-                                   static_cast<long>(
-                                       (config_["interval"].isNumeric() ? config_["interval"].asDouble() : interval) * 1000)))),
+                          (config_["interval"].isNumeric()
+                               ? std::max(1L,  // Minimum 1ms due to millisecond precision
+                                          static_cast<long>(config_["interval"].asDouble()) * 1000)
+                               : 1000 * (long)interval))),
       default_format_(format_) {
   label_.set_name(name);
   if (!id.empty()) {