diff --git a/gpioMonMain.cpp b/gpioMonMain.cpp
index 47c4d39..2a29d1f 100644
--- a/gpioMonMain.cpp
+++ b/gpioMonMain.cpp
@@ -83,7 +83,7 @@
         std::string lineMsg = "GPIO Line ";
 
         /* GPIO line */
-        gpiod_line* line = NULL;
+        gpiod_line* line = nullptr;
 
         /* GPIO line configuration, default to monitor both edge */
         struct gpiod_line_request_config config
@@ -130,7 +130,7 @@
             line = gpiod_line_find(lineName.c_str());
         }
 
-        if (line == NULL)
+        if (line == nullptr)
         {
             lg2::error("Failed to find the {GPIO}", "GPIO", lineMsg);
             continue;
diff --git a/multi-presence/main.cpp b/multi-presence/main.cpp
index 368f8bb..858ac7c 100644
--- a/multi-presence/main.cpp
+++ b/multi-presence/main.cpp
@@ -84,7 +84,7 @@
         std::string lineMsg = "GPIO Line ";
 
         /* GPIO line */
-        gpiod_line* line = NULL;
+        gpiod_line* line = nullptr;
 
         /* GPIO line configuration, default to monitor both edge */
         struct gpiod_line_request_config config
@@ -131,7 +131,7 @@
             line = gpiod_line_find(lineName.c_str());
         }
 
-        if (line == NULL)
+        if (line == nullptr)
         {
             lg2::error("Failed to find the {GPIO}", "GPIO", lineMsg);
             continue;
diff --git a/presence/gpio_presence.hpp b/presence/gpio_presence.hpp
index 3125ba2..52a1653 100644
--- a/presence/gpio_presence.hpp
+++ b/presence/gpio_presence.hpp
@@ -81,7 +81,7 @@
             // DRIVER_BIND_DELAY_MS environment variable is set.
             // Update the bind delay (in milliseconds) to the value from the
             // environment.
-            delay = std::strtoull(envDelay, NULL, 10);
+            delay = std::strtoull(envDelay, nullptr, 10);
         }
         determinePresence();
     }