diff --git a/tools/build_api.py b/tools/build_api.py
index fe0b4c0e8b2..ba89cfa578e 100644
--- a/tools/build_api.py
+++ b/tools/build_api.py
@@ -145,6 +145,8 @@ def get_config(src_paths, target, toolchain_name):
 
         prev_features = features
     toolchain.config.validate_config()
+    if toolchain.config.has_regions:
+        _ = list(toolchain.config.regions)
 
     cfg, macros = toolchain.config.get_config_data()
     features = toolchain.config.get_features()
diff --git a/tools/config/__init__.py b/tools/config/__init__.py
index fd4a2d3d868..aaa5344f4d6 100644
--- a/tools/config/__init__.py
+++ b/tools/config/__init__.py
@@ -17,7 +17,7 @@
 
 from copy import deepcopy
 import os
-from os.path import dirname, abspath
+from os.path import dirname, abspath, exists
 import sys
 from collections import namedtuple
 from os.path import splitext
@@ -506,6 +506,8 @@ def regions(self):
                                   "build a bootloader project")
         if 'target.bootloader_img' in target_overrides:
             filename = target_overrides['target.bootloader_img']
+            if not exists(filename):
+                raise ConfigException("Bootloader %s not found" % filename)
             part = intelhex_offset(filename, offset=rom_start)
             if part.minaddr() != rom_start:
                 raise ConfigException("bootloader executable does not "
diff --git a/tools/test/config_test/test29/mbed_app.json b/tools/test/config_test/test29/mbed_app.json
new file mode 100644
index 00000000000..c2ba944b9d2
--- /dev/null
+++ b/tools/test/config_test/test29/mbed_app.json
@@ -0,0 +1,7 @@
+{
+    "target_overrides": {
+        "K64F": {
+            "target.bootloader_img": "does_not_exists.bin"
+        }
+    }
+}
diff --git a/tools/test/config_test/test29/test_data.py b/tools/test/config_test/test29/test_data.py
new file mode 100644
index 00000000000..935d3d9037a
--- /dev/null
+++ b/tools/test/config_test/test29/test_data.py
@@ -0,0 +1,6 @@
+expected_results = {
+    "K64F": {
+        "desc": "error when bootloader not found",
+        "exception_msg": "not found"
+    }
+}