diff --git a/docs/markdown/snippets/non-unique-target-names.md b/docs/markdown/snippets/non-unique-target-names.md
new file mode 100644
index 000000000..9b3f9173c
--- /dev/null
+++ b/docs/markdown/snippets/non-unique-target-names.md
@@ -0,0 +1,9 @@
+## Relaxing of target name requirements
+
+In earlier versions of Meson you could only have one target of a given name for each type.
+For example you could not have two executables named `foo`. This requirement is now
+relaxed so that you can have multiple targets with the same name, as long as they are in
+different subdirectories.
+
+Note that projects that have multiple targets with the same name can not be built with
+the `flat` layout or any backend that writes outputs in the same directory.
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 47c40a242..e70705376 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -310,11 +310,16 @@ a hard error in the future.''' % name)
     def get_id(self):
         # This ID must also be a valid file name on all OSs.
         # It should also avoid shell metacharacters for obvious
-        # reasons.
-        base = self.name + self.type_suffix()
-        if self.subproject == '':
-            return base
-        return self.subproject + '@@' + base
+        # reasons. '@' is not used as often as '_' in source code names.
+        # In case of collisions consider using checksums.
+        # FIXME replace with assert when slash in names is prohibited
+        name_part = self.name.replace('/', '@').replace('\\', '@')
+        assert not has_path_sep(self.type_suffix())
+        myid = name_part + self.type_suffix()
+        if self.subdir:
+            subdir_part = self.subdir.replace('/', '@').replace('\\', '@')
+            myid = subdir_part + '@@' + myid
+        return myid
 
     def process_kwargs(self, kwargs):
         if 'build_by_default' in kwargs:
diff --git a/run_unittests.py b/run_unittests.py
index 19a8c87f4..775fd310b 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -1117,7 +1117,7 @@ class AllPlatformTests(BasePlatformTests):
         incs = [a for a in shlex.split(execmd) if a.startswith("-I")]
         self.assertEqual(len(incs), 9)
         # target private dir
-        self.assertPathEqual(incs[0], "-Isub4/someexe@exe")
+        self.assertPathEqual(incs[0], "-Isub4/sub4@@someexe@exe")
         # target build subdir
         self.assertPathEqual(incs[1], "-Isub4")
         # target source subdir
@@ -1917,6 +1917,15 @@ int main(int argc, char **argv) {
         self.init(testdir, extra_args=['--layout=flat'])
         self.build()
 
+    def test_identical_target_name_in_subdir_flat_layout(self):
+        '''
+        Test that identical targets in different subdirs do not collide
+        if layout is flat.
+        '''
+        testdir = os.path.join(self.common_test_dir, '189 same target name flat layout')
+        self.init(testdir, extra_args=['--layout=flat'])
+        self.build()
+
     def test_flock(self):
         exception_raised = False
         with tempfile.TemporaryDirectory() as tdir:
@@ -2601,8 +2610,8 @@ class LinuxlikeTests(BasePlatformTests):
     def test_unity_subproj(self):
         testdir = os.path.join(self.common_test_dir, '49 subproject')
         self.init(testdir, extra_args='--unity=subprojects')
-        self.assertPathExists(os.path.join(self.builddir, 'subprojects/sublib/sublib@@simpletest@exe/simpletest-unity.c'))
-        self.assertPathExists(os.path.join(self.builddir, 'subprojects/sublib/sublib@@sublib@sha/sublib-unity.c'))
+        self.assertPathExists(os.path.join(self.builddir, 'subprojects/sublib/subprojects@sublib@@simpletest@exe/simpletest-unity.c'))
+        self.assertPathExists(os.path.join(self.builddir, 'subprojects/sublib/subprojects@sublib@@sublib@sha/sublib-unity.c'))
         self.assertPathDoesNotExist(os.path.join(self.builddir, 'user@exe/user-unity.c'))
         self.build()
 
diff --git a/test cases/failing/17 same name/file.c b/test cases/common/183 same target name/file.c
similarity index 100%
rename from test cases/failing/17 same name/file.c
rename to test cases/common/183 same target name/file.c
diff --git a/test cases/failing/17 same name/meson.build b/test cases/common/183 same target name/meson.build
similarity index 100%
rename from test cases/failing/17 same name/meson.build
rename to test cases/common/183 same target name/meson.build
diff --git a/test cases/failing/17 same name/sub/file2.c b/test cases/common/183 same target name/sub/file2.c
similarity index 100%
rename from test cases/failing/17 same name/sub/file2.c
rename to test cases/common/183 same target name/sub/file2.c
diff --git a/test cases/failing/17 same name/sub/meson.build b/test cases/common/183 same target name/sub/meson.build
similarity index 100%
rename from test cases/failing/17 same name/sub/meson.build
rename to test cases/common/183 same target name/sub/meson.build
diff --git a/test cases/common/189 same target name flat layout/foo.c b/test cases/common/189 same target name flat layout/foo.c
new file mode 100644
index 000000000..ed427899a
--- /dev/null
+++ b/test cases/common/189 same target name flat layout/foo.c	
@@ -0,0 +1 @@
+int meson_test_main_foo(void) { return 10; }
diff --git a/test cases/common/189 same target name flat layout/main.c b/test cases/common/189 same target name flat layout/main.c
new file mode 100644
index 000000000..6f02aeb82
--- /dev/null
+++ b/test cases/common/189 same target name flat layout/main.c	
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int meson_test_main_foo(void);
+int meson_test_subproj_foo(void);
+
+int main(void) {
+    if (meson_test_main_foo() != 10) {
+        printf("Failed meson_test_main_foo\n");
+        return 1;
+    }
+    if (meson_test_subproj_foo() != 20) {
+        printf("Failed meson_test_subproj_foo\n");
+        return 1;
+    }
+    return 0;
+}
diff --git a/test cases/common/189 same target name flat layout/meson.build b/test cases/common/189 same target name flat layout/meson.build
new file mode 100644
index 000000000..a3c95fa25
--- /dev/null
+++ b/test cases/common/189 same target name flat layout/meson.build	
@@ -0,0 +1,11 @@
+project('subdir targets', 'c')
+
+# Idea behind this test is to create targets with identical name
+# but different output files. We can do this by choosing different
+# name_prefix of libraries. Target id does not depend on name_prefix.
+
+main_foo = static_library('foo', 'foo.c', name_prefix : 'main')
+subdir('subdir') # defines subdir_foo
+
+exe = executable('prog', 'main.c', link_with : [main_foo, subdir_foo])
+test('main test', exe)
diff --git a/test cases/common/189 same target name flat layout/subdir/foo.c b/test cases/common/189 same target name flat layout/subdir/foo.c
new file mode 100644
index 000000000..f33429229
--- /dev/null
+++ b/test cases/common/189 same target name flat layout/subdir/foo.c	
@@ -0,0 +1 @@
+int meson_test_subproj_foo(void) { return 20; }
diff --git a/test cases/common/189 same target name flat layout/subdir/meson.build b/test cases/common/189 same target name flat layout/subdir/meson.build
new file mode 100644
index 000000000..223a5ef90
--- /dev/null
+++ b/test cases/common/189 same target name flat layout/subdir/meson.build	
@@ -0,0 +1 @@
+subdir_foo = static_library('foo', 'foo.c', name_prefix : 'subdir')
diff --git a/test cases/failing/17 same target/file.c b/test cases/failing/17 same target/file.c
new file mode 100644
index 000000000..741237235
--- /dev/null
+++ b/test cases/failing/17 same target/file.c	
@@ -0,0 +1 @@
+int func() { return 0; }
diff --git a/test cases/failing/17 same target/meson.build b/test cases/failing/17 same target/meson.build
new file mode 100644
index 000000000..ee586d0f4
--- /dev/null
+++ b/test cases/failing/17 same target/meson.build	
@@ -0,0 +1,4 @@
+project('same target', 'c')
+
+static_library('foo', 'file.c')
+static_library('foo', 'file.c')