diff --git a/gpio-util/main.cpp b/gpio-util/main.cpp
index 0cfacf4..82cbed4 100644
--- a/gpio-util/main.cpp
+++ b/gpio-util/main.cpp
@@ -177,7 +177,7 @@
     {
         function->second(gpio, delay);
     }
-    catch (std::runtime_error& e)
+    catch (const std::runtime_error& e)
     {
         std::cerr << e.what();
         return -1;