diff --git a/testing/scenario_app/build_and_run_android_tests.sh b/testing/scenario_app/build_and_run_android_tests.sh
index 5232c1c1484..3f10102be1c 100755
--- a/testing/scenario_app/build_and_run_android_tests.sh
+++ b/testing/scenario_app/build_and_run_android_tests.sh
@@ -43,6 +43,7 @@ if [[ ! -d "$SRC_DIR/out/$FLUTTER_ENGINE" ]]; then
 fi
 
 autoninja -C "$SRC_DIR/out/$FLUTTER_ENGINE"
+autoninja -C "$SRC_DIR/out/host_debug_unopt"
 
 "$SCRIPT_DIR/compile_android_jit.sh" "$SRC_DIR/out/host_debug_unopt" "$SRC_DIR/out/$FLUTTER_ENGINE/clang_x64"
 "$SCRIPT_DIR/run_android_tests.sh" "$FLUTTER_ENGINE"
diff --git a/testing/scenario_app/build_and_run_ios_tests.sh b/testing/scenario_app/build_and_run_ios_tests.sh
index 0ee0d3a6beb..4f9b92c5f96 100755
--- a/testing/scenario_app/build_and_run_ios_tests.sh
+++ b/testing/scenario_app/build_and_run_ios_tests.sh
@@ -42,6 +42,7 @@ if [ ! -d "$SRC_DIR/out/$FLUTTER_ENGINE" ]; then
 fi
 
 autoninja -C "$SRC_DIR/out/$FLUTTER_ENGINE"
+autoninja -C "$SRC_DIR/out/host_debug_unopt"
 
 "$SCRIPT_DIR/compile_ios_jit.sh" "$SRC_DIR/out/host_debug_unopt" "$SRC_DIR/out/$FLUTTER_ENGINE/clang_x64"
 "$SCRIPT_DIR/run_ios_tests.sh" "$FLUTTER_ENGINE"