diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0c813b86..ca600935 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -63,11 +63,11 @@ if (NOT ARCH OR ARCH STREQUAL "" OR ARCH STREQUAL "native" OR ARCH STREQUAL "def
 else()
   set(ARCH_ID "${ARCH}")
 endif()
-string(TOLOWER ${ARCH_ID} ARM_ID)
-string(SUBSTRING ${ARCH_ID} 0 3 ARM_TEST)
+string(TOLOWER "${ARCH_ID}" ARM_ID)
+string(SUBSTRING "${ARCH_ID}" 0 3 ARM_TEST)
 if (ARM_TEST STREQUAL "arm")
   set(ARM 1)
-  string(SUBSTRING ${ARCH_ID} 0 5 ARM_TEST)
+  string(SUBSTRING "${ARCH_ID}" 0 5 ARM_TEST)
   if (ARM_TEST STREQUAL "armv6")
     set(ARM6 1)
   endif()