diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index 2d86728..44947b1 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -105,7 +105,7 @@ jobs:
           CARGO_PROFILE_RELEASE_OPT_LEVEL: 3
           CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS: false
           RUSTC_BOOTSTRAP: 1
-          RUSTFLAGS: -Cforce-unwind-tables=yes -Cembed-bitcode=yes
+          RUSTFLAGS: -Cforce-unwind-tables=yes -Cembed-bitcode=yes -Zforce-unstable-if-unmarked=yes
           __CARGO_DEFAULT_LIB_METADATA: stablestd
           CC: riscv-none-elf-gcc
           AR: riscv-none-elf-ar
diff --git a/build.ps1 b/build.ps1
index 8b45ff3..d25664b 100644
--- a/build.ps1
+++ b/build.ps1
@@ -34,7 +34,7 @@ $env:CARGO_PROFILE_RELEASE_DEBUG = 0
 $env:CARGO_PROFILE_RELEASE_OPT_LEVEL = ""
 $env:CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS = "true"
 $env:RUSTC_BOOTSTRAP = 1
-$env:RUSTFLAGS = "-Cforce-unwind-tables=yes -Cembed-bitcode=yes"
+$env:RUSTFLAGS = "-Cforce-unwind-tables=yes -Cembed-bitcode=yes -Zforce-unstable-if-unmarked=yes"
 $env:__CARGO_DEFAULT_LIB_METADATA = "stablestd"
 
 # Set up the C compiler. We need to explicitly specify these variables
diff --git a/build.sh b/build.sh
index a0d1b76..0cc2963 100755
--- a/build.sh
+++ b/build.sh
@@ -33,7 +33,7 @@ export CARGO_PROFILE_RELEASE_DEBUG=0
 export CARGO_PROFILE_RELEASE_OPT_LEVEL="3"
 export CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS="true"
 export RUSTC_BOOTSTRAP=1
-export RUSTFLAGS="-Cforce-unwind-tables=yes -Cembed-bitcode=yes"
+export RUSTFLAGS="-Cforce-unwind-tables=yes -Cembed-bitcode=yes -Zforce-unstable-if-unmarked=yes"
 export __CARGO_DEFAULT_LIB_METADATA="stablestd"
 
 command_exists() {
diff --git a/rebuild.sh b/rebuild.sh
index aece135..c1a6d64 100644
--- a/rebuild.sh
+++ b/rebuild.sh
@@ -36,7 +36,7 @@ export CARGO_PROFILE_RELEASE_DEBUG=0
 export CARGO_PROFILE_RELEASE_OPT_LEVEL="3"
 export CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS="true"
 export RUSTC_BOOTSTRAP=1
-export RUSTFLAGS="-Cforce-unwind-tables=yes -Cembed-bitcode=yes"
+export RUSTFLAGS="-Cforce-unwind-tables=yes -Cembed-bitcode=yes -Zforce-unstable-if-unmarked=yes"
 export __CARGO_DEFAULT_LIB_METADATA="stablestd"
 
 command_exists() {