diff --git a/include/openssl/thread.h b/include/openssl/thread.h
index 98073b0..91706fe 100644
--- a/include/openssl/thread.h
+++ b/include/openssl/thread.h
@@ -66,7 +66,7 @@
 #endif
 
 
-#if defined(OPENSSL_NO_THREADS)
+#if !defined(OPENSSL_THREADS)
 typedef struct crypto_mutex_st {
   char padding;  // Empty structs have different sizes in C and C++.
 } CRYPTO_MUTEX;