diff --git a/contrib/cross-aarch64-android.cmake b/contrib/cross-aarch64-android.cmake
index 8ed84b1d6..efd004f10 100644
--- a/contrib/cross-aarch64-android.cmake
+++ b/contrib/cross-aarch64-android.cmake
@@ -26,8 +26,8 @@ set(CMAKE_CXX_COMPILER "aarch64-linux-android-g++")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 #-nostdlib
diff --git a/contrib/cross-aarch64.cmake b/contrib/cross-aarch64.cmake
index c8d880d63..894ffedf0 100644
--- a/contrib/cross-aarch64.cmake
+++ b/contrib/cross-aarch64.cmake
@@ -26,8 +26,8 @@ set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 #-nostdlib
diff --git a/contrib/cross-arm-android-gnueabi.cmake b/contrib/cross-arm-android-gnueabi.cmake
index da9aaae60..11515d8bb 100644
--- a/contrib/cross-arm-android-gnueabi.cmake
+++ b/contrib/cross-arm-android-gnueabi.cmake
@@ -30,8 +30,8 @@ set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-androideabi-g++")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 # Where to look for the target environment. (More paths can be added here)
diff --git a/contrib/cross-arm-linux-gnueabihf.cmake b/contrib/cross-arm-linux-gnueabihf.cmake
index 289f27a5a..df8c1c3cd 100644
--- a/contrib/cross-arm-linux-gnueabihf.cmake
+++ b/contrib/cross-arm-linux-gnueabihf.cmake
@@ -27,8 +27,8 @@ set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-gnueabihf-g++")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 # Where to look for the target environment. (More paths can be added here)
diff --git a/contrib/cross-esp32.cmake b/contrib/cross-esp32.cmake
index 2c8996b74..42882b5d5 100644
--- a/contrib/cross-esp32.cmake
+++ b/contrib/cross-esp32.cmake
@@ -27,8 +27,8 @@ set(CMAKE_LINKER	"${CROSS_PATH}/bin/xtensa-esp32-elf-ld${EXECUTABLE_EXT}")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 SET(CMAKE_C_FLAGS "-nostdlib -Wall -Werror \
diff --git a/contrib/cross-ming.cmake b/contrib/cross-ming.cmake
index 1b2101458..a2cca4823 100644
--- a/contrib/cross-ming.cmake
+++ b/contrib/cross-ming.cmake
@@ -30,8 +30,8 @@ set(CMAKE_C_FLAGS "-Wno-error")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 # Where to look for the target environment. (More paths can be added here)
diff --git a/contrib/cross-w32.cmake b/contrib/cross-w32.cmake
index 05128857b..46a7aa646 100644
--- a/contrib/cross-w32.cmake
+++ b/contrib/cross-w32.cmake
@@ -29,8 +29,8 @@ set(CMAKE_C_FLAGS "-Wno-error")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 # Where to look for the target environment. (More paths can be added here)
diff --git a/contrib/cross-w64.cmake b/contrib/cross-w64.cmake
index 4fff88256..ead6da1be 100644
--- a/contrib/cross-w64.cmake
+++ b/contrib/cross-w64.cmake
@@ -29,8 +29,8 @@ set(CMAKE_C_FLAGS "-Wno-error")
 # optimizations with -O3.
 #
 if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
-	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} -O2)
-	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} -O2)
+	set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
 endif()
 
 # Where to look for the target environment. (More paths can be added here)