diff --git a/vxworks-6.9/target/src/openssl/openssl_src/vxworks.krnl.mak b/vxworks-6.9/target/src/openssl/openssl_src/vxworks.krnl.mak
index f06d150c..813fee3a 100644
--- a/vxworks-6.9/target/src/openssl/openssl_src/vxworks.krnl.mak
+++ b/vxworks-6.9/target/src/openssl/openssl_src/vxworks.krnl.mak
@@ -30,7 +30,7 @@ VX_CFLAGS += -mcpu=cortex-a7
 endif
 endif
 
-OPENSSL_CPPFLAGS = -DOPENSSL_SYS_VXWORKS_SUPPORT
+OPENSSL_CPPFLAGS = -DOPENSSL_SYS_VXWORKS_SUPPORT -DOPENSSL_NO_THREAD_POOL
 
 OPENSSL_CONFIGURE_OPTIONS = no-shared