diff --git a/distribution/changelog.txt b/distribution/changelog.txt
index 595b1f6f63..abde4d2937 100644
--- a/distribution/changelog.txt
+++ b/distribution/changelog.txt
@@ -18,6 +18,7 @@
 - Fix: [#6193] All rings in Space Rings use the same secondary colour
 - Fix: [#6198] You cannot cancel RCT1 directory selection
 - Fix: [#6271] Wrong booster speed tooltip text
+- Fix: [#6320] Crash when CSS1.DAT is absent
 - Fix: Infinite loop when removing scenery elements with >127 base height.
 - Fix: Ghosting of transparent map elements when the viewport is moved in OpenGL mode.
 - Improved: [#6186] Transparent menu items now draw properly in OpenGL mode.
diff --git a/src/openrct2-ui/audio/AudioChannel.cpp b/src/openrct2-ui/audio/AudioChannel.cpp
index 50a63cdb65..92dba6358e 100644
--- a/src/openrct2-ui/audio/AudioChannel.cpp
+++ b/src/openrct2-ui/audio/AudioChannel.cpp
@@ -248,7 +248,8 @@ namespace OpenRCT2 { namespace Audio
         AudioFormat GetFormat() const override
         {
             AudioFormat result = { 0 };
-            if (_source != nullptr)
+            // The second check is there because NullAudioSource does not implement GetFormat. Avoid calling it.
+            if (_source != nullptr && _source->GetLength() > 0)
             {
                 result = _source->GetFormat();
             }