diff --git a/hdr/BCM2835 b/hdr/BCM2835
index 8fb0570dabd5ee14f8dd4825d501a2c2a78ffff8..ab98c2fa25ddd9ad15dd973fcdc51fb21d452105 100644
--- a/hdr/BCM2835
+++ b/hdr/BCM2835
@@ -391,6 +391,7 @@ GPAFEDE1     *        &8c            ; GPIO Async falling edge detect enable 1
 GPPUPDEN     *        &94            ; GPIO PullUp PullDown Enable
 GPPUDCK0     *        &98            ; GPIO PullUp PullDown Clock 0
 GPPUDCK1     *        &9c            ; GPIO PullUp PullDown Clock 1
+GPPinMuxSD   *        &d0
 
 ; Auxio peripherals
 ; MiniUart uses TXD1 and RXD1
diff --git a/s/SDIO b/s/SDIO
index 1f48ef17d461983b01208db80d47e9141946c0fd..76cf533dd92e145bcc7358e184d36c1a187f99b6 100644
--- a/s/SDIO
+++ b/s/SDIO
@@ -319,6 +319,17 @@ SDHCI   HALDeviceField GetWriteProtect
         ; Init the SDHCI HAL device
 SDIO_InitDevices ROUT
         Push    "lr"
+
+        CPUDetect a1
+        BLS     %FT00
+        ; Pi 4 setup - select legacy emmc controller for now
+        LDR     a1, PeriBase
+        MOV     a2, #3
+        ADD     a1, a1, #GPIO_Base
+        DoMemBarrier lr
+        STR     a2, [a1, #GPPinMuxSD]
+        DoMemBarrier lr
+00
         BL      MeasureSpeed
 
         ADR     a1, SDHCIDevice