diff --git a/CMakeLists.txt b/CMakeLists.txt
index ebd8260af5..e457a3499d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,6 +38,7 @@ option(LIBRESSL_TESTS "Build tests" ON)
 option(ENABLE_ASM "Enable assembly" ON)
 option(ENABLE_EXTRATESTS "Enable extra tests that may be unreliable on some platforms" OFF)
 option(ENABLE_NC "Enable installing TLS-enabled nc(1)" OFF)
+option(ENABLE_SPECTRE_MITIGATION "Enable MSVC Spectre mitigation" OFF)
 set(OPENSSLDIR ${OPENSSLDIR} CACHE PATH "Set the default openssl directory" FORCE)
 set(LIBRESSL_INSTALL_CMAKEDIR "${CMAKE_INSTALL_LIBDIR}/cmake/LibreSSL" CACHE STRING "Installation directory for the CMake targets")
 
@@ -150,6 +151,13 @@ if(MSVC)
 	add_definitions(-Dinline=__inline)
 	message(STATUS "Using [${CMAKE_C_COMPILER_ID}] compiler")
 
+	if(ENABLE_SPECTRE_MITIGATION)
+		if(MSVC_VERSION LESS 1912)
+			message(FATAL_ERROR "Spectre mitigation unavailable before MSVC 2017 15.5")
+		endif()
+		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Qspectre")
+	endif()
+
 	include(TestBigEndian)
 	TEST_BIG_ENDIAN(HAVE_BIG_ENDIAN)
 	if(HAVE_BIG_ENDIAN)