diff --git a/userspace/libsinsp/sinsp.cpp b/userspace/libsinsp/sinsp.cpp
index c3d5a1f4ec..00819ae4ab 100644
--- a/userspace/libsinsp/sinsp.cpp
+++ b/userspace/libsinsp/sinsp.cpp
@@ -1661,7 +1661,7 @@ void sinsp::start_dropping_mode(uint32_t sampling_ratio)
 }
 #endif // _WIN32
 
-void sinsp::set_filter(std::unique_ptr<sinsp_filter> filter, const std::optional<std::string>& filterstring)
+void sinsp::set_filter(std::unique_ptr<sinsp_filter> filter, const std::string& filterstring)
 {
 	if(m_filter != NULL)
 	{
@@ -1670,7 +1670,7 @@ void sinsp::set_filter(std::unique_ptr<sinsp_filter> filter, const std::optional
 	}
 
 	m_filter = std::move(filter);
-	m_filterstring = filterstring.value_or("");
+	m_filterstring = filterstring;
 }
 
 void sinsp::set_filter(const std::string& filter)
diff --git a/userspace/libsinsp/sinsp.h b/userspace/libsinsp/sinsp.h
index 33e92ce37e..d67cb4bb1f 100644
--- a/userspace/libsinsp/sinsp.h
+++ b/userspace/libsinsp/sinsp.h
@@ -303,7 +303,7 @@ class SINSP_PUBLIC sinsp : public capture_stats_source
 
 	  \param filter the runtime filter object
 	*/
-	void set_filter(std::unique_ptr<sinsp_filter> filter, const std::optional<std::string>& filterstring);
+	void set_filter(std::unique_ptr<sinsp_filter> filter, const std::string& filterstring = "");
 
 	/*!
 	  \brief Return the filter set for this capture.