diff --git a/CMakeLists.txt b/CMakeLists.txt
index cfd0e2591..27520bfff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -193,6 +193,14 @@ aws_set_common_properties(${PROJECT_NAME} NO_WEXTRA)
 aws_prepare_symbol_visibility_args(${PROJECT_NAME} "AWS_COMMON")
 target_compile_options(${PROJECT_NAME} PUBLIC ${PLATFORM_CFLAGS})
 
+if (NOT USE_CPU_EXTENSIONS)
+    target_compile_definitions(${PROJECT_NAME} PUBLIC -DHAS_CPU_EXTENSTIONS=0)
+    message(STATUS "Adding -DHAS_CPU_EXTENSTIONS=0 to target ${PROJECT_NAME}")
+else ()
+    target_compile_definitions(${PROJECT_NAME} PUBLIC -DHAS_CPU_EXTENSTIONS=1)
+    message(STATUS "Adding -DHAS_CPU_EXTENSTIONS=1 to target ${PROJECT_NAME}")
+endif ()
+
 # Check public headers, to ensure they're safe for any 3rdparty to include
 set(HEADERS_TO_CHECK ${AWS_COMMON_HEADERS})
 
diff --git a/source/encoding.c b/source/encoding.c
index 5b854c014..5027faaca 100644
--- a/source/encoding.c
+++ b/source/encoding.c
@@ -9,7 +9,7 @@
 #include <ctype.h>
 #include <stdlib.h>
 
-#ifdef USE_SIMD_ENCODING
+#if defined(USE_SIMD_ENCODING) && HAS_CPU_EXTENSTIONS
 size_t aws_common_private_base64_decode_sse41(const unsigned char *in, unsigned char *out, size_t len);
 void aws_common_private_base64_encode_sse41(
     const unsigned char *in,