diff --git a/pcsx-redux.nix b/pcsx-redux.nix
index 26a62d33..74b72e7c 100644
--- a/pcsx-redux.nix
+++ b/pcsx-redux.nix
@@ -126,8 +126,8 @@ let
     ({
       owner = "pcsx-redux";
       repo = "nugget";
-      rev = "4dac78a47eee88c6246856d071769c44ad43f0c9";
-      hash = "sha256-6qhjs5dTrtwtW4TByc2kPcYULCrDsOUR11awDXBVaX4=";
+      rev = "d9e0baca03c5ae6c292b1daf50515d19d370dd33";
+      hash = "sha256-8TZG8AQ4wUGz0TegUKThR+rUqaAS9xoy5yKKl2sKgGo=";
       dest = "src/mips";
     })
     ({
diff --git a/src/core/cdrom.cc b/src/core/cdrom.cc
index 556ce3f1..4dac7e10 100644
--- a/src/core/cdrom.cc
+++ b/src/core/cdrom.cc
@@ -293,13 +293,15 @@ class CDRomImpl final : public PCSX::CDRom {
     void scheduleDMA(uint32_t cycles) { PCSX::g_emulator->m_cpu->schedule(PCSX::Schedule::CDRDMA, cycles); }
     void scheduleDMA(std::chrono::nanoseconds delay) { scheduleDMA(PCSX::psxRegisters::durationToCycles(delay)); }
 
+    // An acknowledged response no longer holds its slot: its unread bytes stay readable
+    // until the next response replaces them.
     bool maybeEnqueueResponse(QueueElement &response) {
         if (m_responseFifo[0].valueEmpty() && !m_responseFifo[1].empty()) {
             m_responseFifo[0] = m_responseFifo[1];
             m_responseFifo[1] = response;
             return true;
         }
-        if (m_responseFifo[0].empty()) {
+        if (m_responseFifo[0].valueEmpty()) {
             m_responseFifo[0] = response;
             return true;
         } else if (m_responseFifo[1].empty()) {
diff --git a/src/core/cdrom.h b/src/core/cdrom.h
index eea08b09..3ea48b23 100644
--- a/src/core/cdrom.h
+++ b/src/core/cdrom.h
@@ -221,7 +221,7 @@ class CDRom {
     QueueElement m_commandFifo;
     QueueElement m_commandExecuting;
     QueueElement m_responseFifo[2];
-    bool responseFifoFull() { return !m_responseFifo[0].empty() && !m_responseFifo[1].empty(); }
+    bool responseFifoFull() { return !m_responseFifo[0].valueEmpty() && !m_responseFifo[1].empty(); }
 
   private:
     friend class Widgets::IsoBrowser;
diff --git a/src/mips b/src/mips
index 4dac78a4..d9e0baca 160000
--- a/src/mips
+++ b/src/mips
@@ -1 +1 @@
-Subproject commit 4dac78a47eee88c6246856d071769c44ad43f0c9
+Subproject commit d9e0baca03c5ae6c292b1daf50515d19d370dd33
diff --git a/tests/pcsxrunner/cdrom.cc b/tests/pcsxrunner/cdrom.cc
index 989fae0c..9af227b7 100644
--- a/tests/pcsxrunner/cdrom.cc
+++ b/tests/pcsxrunner/cdrom.cc
@@ -32,4 +32,41 @@ TEST(cdrom, Dynarec) {
                         "test.cue", "-loadexe", "src/mips/tests/cdrom/cdrom.ps-exe");
     int ret = invoker.invoke();
     EXPECT_EQ(ret, 0);
-}
\ No newline at end of file
+}
+// Boots the test disc through OpenBIOS's shell and kernel loader, with no -loadexe. Passes once
+// the disc's boot executable is in RAM and the CPU is running inside it, fails after 6000 frames.
+static const char c_discBoot[] = R"(
+local f = assert(io.open('src/mips/monitor/hosts/retail/monitor-retail.ps-exe', 'rb'))
+local exe = f:read('*a')
+f:close()
+local function u32(o)
+    local a, b, c, d = exe:byte(o + 1, o + 4)
+    return a + b * 0x100 + c * 0x10000 + d * 0x1000000
+end
+local tAddr, tSize = u32(0x18), u32(0x1c)
+local text = exe:sub(0x801, 0x800 + tSize)
+local frames = 0
+DiscBootListener = PCSX.Events.createEventListener('GPU::Vsync', function()
+    frames = frames + 1
+    local pc = PCSX.getRegisters().pc
+    if pc >= tAddr and pc < tAddr + tSize then
+        local ram = ffi.string(PCSX.getMemPtr() + bit.band(tAddr, 0x1fffff), tSize)
+        if ram == text then PCSX.quit(0) end
+    end
+    if frames >= 6000 then PCSX.quit(1) end
+end)
+)";
+
+TEST(cdrom, OpenBIOSBootsDiscInterpreter) {
+    MainInvoker invoker("-no-ui", "-run", "-bios", "src/mips/openbios/openbios.bin", "-testmode", "-interpreter",
+                        "-iso", "test.cue", "-exec", c_discBoot);
+    int ret = invoker.invoke();
+    EXPECT_EQ(ret, 0);
+}
+
+TEST(cdrom, OpenBIOSBootsDiscDynarec) {
+    MainInvoker invoker("-no-ui", "-run", "-bios", "src/mips/openbios/openbios.bin", "-testmode", "-dynarec", "-iso",
+                        "test.cue", "-exec", c_discBoot);
+    int ret = invoker.invoke();
+    EXPECT_EQ(ret, 0);
+}