diff --git a/platformio/builder/tools/piomisc.py b/platformio/builder/tools/piomisc.py
index 5ef48d20..87b3bf12 100644
--- a/platformio/builder/tools/piomisc.py
+++ b/platformio/builder/tools/piomisc.py
@@ -314,17 +314,26 @@ def ConfigureDebugFlags(env):
         if scope not in env:
             return
         unflags = ["-Os", "-g"]
-        for level in [0, 1, 2]:
+        for level in [0, 1, 2, 3]:
             for flag in ("O", "g", "ggdb"):
                 unflags.append("-%s%d" % (flag, level))
         env[scope] = [f for f in env.get(scope, []) if f not in unflags]
 
     env.Append(CPPDEFINES=["__PLATFORMIO_BUILD_DEBUG__"])
 
-    debug_flags = ["-Og", "-g2", "-ggdb2"]
     for scope in ("ASFLAGS", "CCFLAGS", "LINKFLAGS"):
         _cleanup_debug_flags(scope)
-        env.Append(**{scope: debug_flags})
+
+    debug_flags = env.ParseFlags(env.GetProjectOption("debug_build_flags"))
+    env.MergeFlags(debug_flags)
+    optimization_flags = [f for f in debug_flags.get("CCFLAGS", []) if f.startswith(
+        ("-O", "-g"))]
+
+    if optimization_flags:
+        env.AppendUnique(
+            ASFLAGS=optimization_flags,
+            LINKFLAGS=optimization_flags
+        )
 
 
 def ConfigureTestTarget(env):
diff --git a/platformio/project/options.py b/platformio/project/options.py
index 7d4c5a71..f8a50a76 100644
--- a/platformio/project/options.py
+++ b/platformio/project/options.py
@@ -600,6 +600,16 @@ ProjectOptions = OrderedDict(
                 name="debug_tool",
                 description="A name of debugging tool",
             ),
+            ConfigEnvOption(
+                group="debug",
+                name="debug_build_flags",
+                description=(
+                    "Custom debug flags/options for preprocessing, compilation, "
+                    "assembly, and linking processes"
+                ),
+                multiple=True,
+                default=["-Og", "-g2", "-ggdb2"],
+            ),
             ConfigEnvOption(
                 group="debug",
                 name="debug_init_break",
diff --git a/tests/test_builder.py b/tests/test_builder.py
index 9dec2e0f..6e73da0a 100644
--- a/tests/test_builder.py
+++ b/tests/test_builder.py
@@ -112,3 +112,61 @@ int main() {
     assert "-DTMP_MACRO1" not in build_output
     assert "-Os" not in build_output
     assert str(tmpdir) not in build_output
+
+
+def test_debug_default_build_flags(clirunner, validate_cliresult, tmpdir):
+    tmpdir.join("platformio.ini").write(
+        """
+[env:native]
+platform = native
+build_type = debug
+"""
+    )
+
+    tmpdir.mkdir("src").join("main.c").write(
+        """
+int main() {
+}
+"""
+    )
+
+    result = clirunner.invoke(cmd_run, ["--project-dir", str(tmpdir), "--verbose"])
+    validate_cliresult(result)
+    build_output = result.output[result.output.find("Scanning dependencies...") :]
+    for line in build_output.split("\n"):
+        if line.startswith("gcc"):
+            assert all(line.count(flag) == 1 for flag in ("-Og", "-g2", "-ggdb2"))
+            assert all(line.count("-%s%d" % (flag, level)) == 0 for flag in (
+                "O", "g", "ggdb") for level in (0, 1, 3))
+            assert "-Os" not in line
+
+
+def test_debug_custom_build_flags(clirunner, validate_cliresult, tmpdir):
+    custom_debug_build_flags = ("-O3", "-g3", "-ggdb3")
+
+    tmpdir.join("platformio.ini").write(
+        """
+[env:native]
+platform = native
+build_type = debug
+debug_build_flags = %s
+    """
+        % " ".join(custom_debug_build_flags)
+    )
+
+    tmpdir.mkdir("src").join("main.c").write(
+        """
+int main() {
+}
+"""
+    )
+
+    result = clirunner.invoke(cmd_run, ["--project-dir", str(tmpdir), "--verbose"])
+    validate_cliresult(result)
+    build_output = result.output[result.output.find("Scanning dependencies...") :]
+    for line in build_output.split("\n"):
+        if line.startswith("gcc"):
+            assert all(line.count(f) == 1 for f in custom_debug_build_flags)
+            assert all(line.count("-%s%d" % (flag, level)) == 0 for flag in (
+                "O", "g", "ggdb") for level in (0, 1, 2))
+            assert all("-O%s" % optimization not in line for optimization in ("g", "s"))