diff --git a/pngpriv.h b/pngpriv.h
index f878d6dc4..71a5ab456 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -123,7 +123,7 @@
     * Note that gcc-4.9 defines __ARM_NEON instead of __ARM_NEON__, so we
     * check both variants.
     */
-#  if defined(__ARM_NEON__) || defined(__ARM_NEON) && \
+#  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
    defined(PNG_ALIGNED_MEMORY_SUPPORTED)
 #     define PNG_ARM_NEON_OPT 2
 #  else