diff --git a/repos/base-sel4/patches/cmake.patch b/repos/base-sel4/patches/cmake.patch
new file mode 100644
index 0000000000..dc377d9a7e
--- /dev/null
+++ b/repos/base-sel4/patches/cmake.patch
@@ -0,0 +1,14 @@
+Prevent truncation of stdout/stderr on open(O_TRUNC) in cmake.
+
+--- src/kernel/sel4/config.cmake
++++ src/kernel/sel4/config.cmake
+@@ -168,9 +168,6 @@ if(DEFINED KernelDTSList AND (NOT "${KernelDTSList}" STREQUAL ""))
+                 "${device_dest}" --hardware-config "${config_file}" --hardware-schema
+                 "${config_schema}" --yaml --yaml-out "${platform_yaml}" --arch "${KernelArch}"
+                 --addrspace-max "${KernelPaddrUserTop}"
+-            INPUT_FILE /dev/stdin
+-            OUTPUT_FILE /dev/stdout
+-            ERROR_FILE /dev/stderr
+             RESULT_VARIABLE error
+         )
+         if(error)
diff --git a/repos/base-sel4/ports/sel4.hash b/repos/base-sel4/ports/sel4.hash
index 21ef42f0bd..75b061c2ed 100644
--- a/repos/base-sel4/ports/sel4.hash
+++ b/repos/base-sel4/ports/sel4.hash
@@ -1 +1 @@
-4cbe95411a514cec9492e32455db68d8c82b9766
+e6fe0a48d0479e6f7ba8243f3e1e860c7d42407a