diff --git a/test/test_build.py b/test/test_build.py
index 162117c..cc713e2 100644
--- a/test/test_build.py
+++ b/test/test_build.py
@@ -211,6 +211,39 @@ def test_kconfig_add_inline_set_to_no(self, linux, output_dir):
         config = output_dir / "config"
         assert "CONFIG_FOO=n\n" in config.read_text()
 
+    def test_kconfig_add_inline_set_to_int(self, linux, output_dir):
+        build(
+            tree=linux,
+            targets=["config"],
+            kconfig_add=["CONFIG_FOO=1", "CONFIG_BAR=0", "CONFIG_BAZ=128"],
+            output_dir=output_dir,
+        )
+        config = output_dir / "config"
+        text = config.read_text()
+        assert "CONFIG_FOO=1\n" in text
+        assert "CONFIG_BAR=0\n" in text
+        assert "CONFIG_BAZ=128\n" in text
+
+    def test_kconfig_add_inline_set_to_hex(self, linux, output_dir):
+        build(
+            tree=linux,
+            targets=["config"],
+            kconfig_add=["CONFIG_FOO=0xdeadbeef"],
+            output_dir=output_dir,
+        )
+        config = output_dir / "config"
+        assert "CONFIG_FOO=0xdeadbeef\n" in config.read_text()
+
+    def test_kconfig_add_inline_set_to_string(self, linux, output_dir):
+        build(
+            tree=linux,
+            targets=["config"],
+            kconfig_add=['CONFIG_FOO="hello world"'],
+            output_dir=output_dir,
+        )
+        config = output_dir / "config"
+        assert 'CONFIG_FOO="hello world"\n' in config.read_text()
+
     def test_kconfig_add_in_tree(self, linux, output_dir):
         build(
             tree=linux,
@@ -247,6 +280,18 @@ def test_kconfig_add_invalid(self, linux):
         with pytest.raises(tuxmake.exceptions.UnsupportedKconfigFragment):
             build(tree=linux, targets=["config"], kconfig_add=["foo"])
 
+    def test_kconfig_add_rejects_missing_prefix(self, linux):
+        with pytest.raises(tuxmake.exceptions.UnsupportedKconfigFragment):
+            build(tree=linux, targets=["config"], kconfig_add=["FOO=m"])
+
+    def test_kconfig_add_rejects_empty_name(self, linux):
+        with pytest.raises(tuxmake.exceptions.UnsupportedKconfigFragment):
+            build(tree=linux, targets=["config"], kconfig_add=["CONFIG_=y"])
+
+    def test_kconfig_add_rejects_empty_value(self, linux):
+        with pytest.raises(tuxmake.exceptions.UnsupportedKconfigFragment):
+            build(tree=linux, targets=["config"], kconfig_add=["CONFIG_FOO="])
+
     def test_kconfig_from_source_tree(self, linux):
         b = build(tree=linux, targets=["config"], kconfig="config/test.config")
         config = b.output_dir / "config"
diff --git a/tuxmake/target.py b/tuxmake/target.py
index 3f59239..6495ce5 100644
--- a/tuxmake/target.py
+++ b/tuxmake/target.py
@@ -258,16 +258,11 @@ def handle_in_tree_config(self, t):
             return False
 
     def handle_inline_fragment(self, config, frag):
-        accepted_patterns = [
-            r"^CONFIG_\w+=[ymn]$",
-            r"^#\s*CONFIG_\w+\s*is\s*not\s*set\s*$",
-        ]
-        accepted = False
-        for pattern in accepted_patterns:
-            if re.match(pattern, frag):
-                accepted = True
-
-        if not accepted:
+        # Syntax-only check: kconfig (olddefconfig / merge_config.sh) is the real validator.
+        if not (
+            re.match(r"^CONFIG_\w+=.+$", frag)
+            or re.match(r"^#\s*CONFIG_\w+\s*is\s*not\s*set\s*$", frag)
+        ):
             return False
 
         with config.open("a") as f: