diff --git a/lib/hooks/stats.cpp b/lib/hooks/stats.cpp
index 16674f578..215e2f21c 100644
--- a/lib/hooks/stats.cpp
+++ b/lib/hooks/stats.cpp
@@ -206,7 +206,7 @@ public:
 		if (f) {
 			try {
 				format = Stats::lookupFormat(f);
-			} catch (std::invalid_argument &e) {
+			} catch (const std::invalid_argument &e) {
 				throw ConfigError(cfg, "node-config-hook-stats", "Invalid statistic output format: {}", f);
 			}
 		}
diff --git a/src/villas-relay.cpp b/src/villas-relay.cpp
index 9f168d16e..b7e3fc243 100644
--- a/src/villas-relay.cpp
+++ b/src/villas-relay.cpp
@@ -375,7 +375,7 @@ int Relay::protocol_cb(lws *wsi, enum lws_callback_reasons reason, void *user, v
 			try {
 				new (c) RelayConnection(wsi, r->loopback);
 			}
-			catch (InvalidUrlException &e) {
+			catch (const InvalidUrlException &e) {
 				lws_close_reason(wsi, LWS_CLOSE_STATUS_PROTOCOL_ERR, (unsigned char *) "Invalid URL", strlen("Invalid URL"));
 
 				return -1;