diff --git a/bin/kaleidoscope-builder b/bin/kaleidoscope-builder
index 8a92e042..b618b470 100755
--- a/bin/kaleidoscope-builder
+++ b/bin/kaleidoscope-builder
@@ -484,7 +484,7 @@ do_compile_with_builder() {
 	      -build-path "${BUILD_PATH}" \
 	      -ide-version "${ARDUINO_IDE_VERSION}" \
 	      -built-in-libraries "${ARDUINO_PATH}/libraries" \
-	      -prefs compiler.cpp.extra_flags="${ARDUINO_CFLAGS} ${LOCAL_CFLAGS}" \
+	      -prefs "compiler.cpp.extra_flags=$(printf "%q", "${ARDUINO_CFLAGS} ${LOCAL_CFLAGS}")" \
 	      -prefs compiler.path="${COMPILER_PATH}" \
 	      -prefs compiler.c.cmd="${_CMD_CC}" \
 	      -prefs compiler.cpp.cmd="${_CMD_CXX}" \
@@ -503,10 +503,10 @@ do_compile_with_cli() {
 	run_arduino_cli compile \
 		--fqbn "${FQBN}" \
 		--libraries "${KALEIDOSCOPE_DIR}/.."  \
-		--build-path=${BUILD_PATH} \
-		--output-dir=${OUTPUT_PATH} \
-	      --build-properties "compiler.cpp.extra_flags=${ARDUINO_CFLAGS} ${LOCAL_CFLAGS}" \
-	      --build-properties "compiler.path=${COMPILER_PATH}" \
+		--build-path "${BUILD_PATH}" \
+		--output-dir "${OUTPUT_PATH}" \
+	      --build-properties "compiler.cpp.extra_flags=$(printf "%q", "${ARDUINO_CFLAGS} ${LOCAL_CFLAGS}")" \
+	      --build-properties compiler.path="${COMPILER_PATH}" \
 	      --build-properties "compiler.c.cmd=${_CMD_CC}" \
 	      --build-properties "compiler.cpp.cmd=${_CMD_CXX}" \
               --build-properties "compiler.ar.cmd=${_CMD_AR}" \