diff --git a/ci/aarch64-macos-debug.sh b/ci/aarch64-macos-debug.sh
index a0681430dc..7dc60c1f4e 100755
--- a/ci/aarch64-macos-debug.sh
+++ b/ci/aarch64-macos-debug.sh
@@ -49,3 +49,13 @@ stage3-debug/bin/zig build test docs \
   -Dskip-non-native \
   --search-prefix "$PREFIX" \
   --test-timeout 2m
+
+stage3-debug/bin/zig build \
+  --prefix stage4-debug \
+  -Denable-llvm \
+  -Dno-lib \
+  -Dtarget=$TARGET \
+  -Duse-zig-libcxx \
+  -Dversion-string="$(stage3-debug/bin/zig version)"
+
+stage4-debug/bin/zig test ../test/behavior.zig
diff --git a/ci/x86_64-linux-debug-llvm.sh b/ci/x86_64-linux-debug-llvm.sh
index f2812d361e..e3b2b85bb1 100755
--- a/ci/x86_64-linux-debug-llvm.sh
+++ b/ci/x86_64-linux-debug-llvm.sh
@@ -66,3 +66,14 @@ stage3-debug/bin/zig build test docs \
   --zig-lib-dir "$PWD/../lib" \
   -Denable-superhtml \
   --test-timeout 12m
+
+stage3-debug/bin/zig build \
+  --prefix stage4-debug \
+  -Duse-llvm \
+  -Denable-llvm \
+  -Dno-lib \
+  -Dtarget=$TARGET \
+  -Duse-zig-libcxx \
+  -Dversion-string="$(stage3-debug/bin/zig version)"
+
+stage4-debug/bin/zig test ../test/behavior.zig
diff --git a/ci/x86_64-linux-debug.sh b/ci/x86_64-linux-debug.sh
index 668b94b4f7..bd95209b11 100755
--- a/ci/x86_64-linux-debug.sh
+++ b/ci/x86_64-linux-debug.sh
@@ -66,3 +66,13 @@ stage3-debug/bin/zig build test docs \
   --zig-lib-dir "$PWD/../lib" \
   -Denable-superhtml \
   --test-timeout 10m
+
+stage3-debug/bin/zig build \
+  --prefix stage4-debug \
+  -Denable-llvm \
+  -Dno-lib \
+  -Dtarget=$TARGET \
+  -Duse-zig-libcxx \
+  -Dversion-string="$(stage3-debug/bin/zig version)"
+
+stage4-debug/bin/zig test ../test/behavior.zig