diff --git a/package/openssl/Makefile b/package/openssl/Makefile
index d95783aac9..2962c07ed2 100644
--- a/package/openssl/Makefile
+++ b/package/openssl/Makefile
@@ -105,7 +105,7 @@ define Build/Configure
 	)
 endef
 
-TARGET_CFLAGS += $(FPIC)
+TARGET_CFLAGS += $(FPIC) -DOPENSSL_THREADS -pthread -D_REENTRANT -D_THREAD_SAFE -D_THREADSAFE
 
 define Build/Compile
 	# XXX: OpenSSL "make depend" will look for installed headers before its own,