diff --git a/app/Traits/HasSecretManager.php b/app/Traits/HasSecretManager.php
index 621a29ca01..35a9c8da47 100644
--- a/app/Traits/HasSecretManager.php
+++ b/app/Traits/HasSecretManager.php
@@ -172,20 +172,23 @@ trait HasSecretManager
     }
 
     /**
-     * The old escaping puts literal and multiline values in single quotes without escaping. Docker
-     * Compose ends the value at the next quote, so a value with a quote breaks the whole .env file.
+     * The old escaping writes JSON objects and arrays without quotes, so a JSON value with a line
+     * break breaks the whole .env file (#8279). It puts other literal and multiline values in single
+     * quotes without escaping, and Docker Compose ends the value at the next quote.
      */
     private function legacyEnvFileLineIsUnreadable(EnvironmentVariable $environmentVariable): bool
     {
-        if (! $environmentVariable->is_literal && ! $environmentVariable->is_multiline) {
+        $value = $this->resolvedEnvironmentVariableValue($environmentVariable);
+
+        if (! is_string($value)) {
             return false;
         }
 
-        $value = $this->resolvedEnvironmentVariableValue($environmentVariable);
+        if (json_validate($value) && (str_starts_with($value, '{') || str_starts_with($value, '['))) {
+            return str_contains($value, "\n");
+        }
 
-        return is_string($value)
-            && str_contains($value, "'")
-            && ! (json_validate($value) && (str_starts_with($value, '{') || str_starts_with($value, '[')));
+        return ($environmentVariable->is_literal || $environmentVariable->is_multiline) && str_contains($value, "'");
     }
 
     /**
diff --git a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
index a05610f9c6..6e906ba30d 100644
--- a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
+++ b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
@@ -1936,6 +1936,22 @@ it('writes a readable runtime env line for legacy literal values with a single q
     expect($runtimeEnvs)->toContain('LEGACY_QUOTE="it\'s"');
 });
 
+it('writes a readable runtime env line for legacy multiline JSON values', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+    $json = "{\n  \"type\": \"service_account\"\n}";
+
+    $variable = createApplicationEnvironmentVariable($application, ['key' => 'GOOGLE_CREDENTIALS_JSON', 'value' => $json, 'is_multiline' => true, 'is_runtime' => true, 'is_buildtime' => false]);
+    $variable->uses_legacy_escaping = true;
+    $variable->save();
+
+    [$job, $reflection] = makeControlVarFilteringJob($application->fresh(), $server);
+
+    /** @var Collection $runtimeEnvs */
+    $runtimeEnvs = invokeDeploymentJobMethod($job, $reflection, 'generate_runtime_environment_variables');
+
+    expect($runtimeEnvs)->toContain('GOOGLE_CREDENTIALS_JSON='.escapeComposeEnvFileValue($json));
+});
+
 it('keeps the old runtime env format for preview variables saved before exact escaping', function () {
     [$application, $server] = makeDeploymentControlVarFixture();
 
diff --git a/tests/Feature/EnvironmentVariableLegacyEscapingTest.php b/tests/Feature/EnvironmentVariableLegacyEscapingTest.php
index 6823dfc7b5..23930493b4 100644
--- a/tests/Feature/EnvironmentVariableLegacyEscapingTest.php
+++ b/tests/Feature/EnvironmentVariableLegacyEscapingTest.php
@@ -129,6 +129,19 @@ test('legacy literal and multiline variables with a single quote get a line that
         ->and($this->service->legacyEscapingChangesValue($literal))->toBeFalse();
 });
 
+test('legacy multiline json variables get a line that docker compose can read', function (array $flags) {
+    $json = "{\n  \"type\": \"service_account\"\n}";
+    $multiline = legacyVariable($this->service, ['key' => 'GOOGLE_CREDENTIALS_JSON', 'value' => $json, ...$flags]);
+    $singleLine = legacyVariable($this->service, ['key' => 'SINGLE_LINE_JSON', 'value' => '{"a":"b"}', ...$flags]);
+
+    expect($this->service->composeEnvironmentFileLine($multiline))->toBe("GOOGLE_CREDENTIALS_JSON=\"{\n  \\\"type\\\": \\\"service_account\\\"\n}\"")
+        ->and($this->service->composeEnvironmentFileLine($singleLine))->toBe('SINGLE_LINE_JSON={"a":"b"}')
+        ->and($this->service->legacyEscapingChangesValue($multiline))->toBeFalse();
+})->with([
+    'multiline' => [['is_multiline' => true]],
+    'plain' => [[]],
+]);
+
 test('legacy database variables keep the old compose environment format', function () {
     $database = StandalonePostgresql::forceCreate([
         'uuid' => 'postgres-legacy-test',