diff --git a/crypto/internal.h b/crypto/internal.h
index b288583..03bb779 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -492,8 +492,9 @@
 // Reference counting.
 
 // Automatically enable C11 atomics if implemented.
-#if !defined(OPENSSL_C11_ATOMIC) && !defined(__STDC_NO_ATOMICS__) && \
-    defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#if !defined(OPENSSL_C11_ATOMIC) && defined(OPENSSL_THREADS) &&   \
+    !defined(__STDC_NO_ATOMICS__) && defined(__STDC_VERSION__) && \
+    __STDC_VERSION__ >= 201112L
 #define OPENSSL_C11_ATOMIC
 #endif