diff --git a/builder/frameworks/arduino/nrf5.py b/builder/frameworks/arduino/nrf5.py
index 56af0bf..60a540b 100644
--- a/builder/frameworks/arduino/nrf5.py
+++ b/builder/frameworks/arduino/nrf5.py
@@ -182,6 +182,15 @@
         env.Exit(1)
 
     if selected_bl:
+        # Validate required bootloader fields
+        required_fields = ["bootloader_file", "linker_script", "max_size", "max_ram_size"]
+        missing_fields = [field for field in required_fields if field not in selected_bl]
+        if missing_fields:
+            sys.stderr.write(
+                "Error. Bootloader '%s' is missing required fields: %s\n" %
+                (selected_bl.get("name", "unknown"), ", ".join(missing_fields)))
+            env.Exit(1)
+
         # Use bootloader_file, linker_script, max_size, max_ram_size from selected_bl
         env.Replace(BOOTLOADERHEX=join(FRAMEWORK_DIR, "variants", board.get("build.variant", ""), selected_bl["bootloader_file"]))
         if "flags" in selected_bl: