diff --git a/changes/bug27781 b/changes/bug27781
new file mode 100644
index 0000000000..44d838af8a
--- /dev/null
+++ b/changes/bug27781
@@ -0,0 +1,4 @@
+  o Major bugfixes (compilation):
+    - Fix compilation on arm (and other less-used CPUs)
+      when compiling with OpenSSL before 1.1. Fixes bug 27781;
+      bugfix on 0.3.4.1-alpha.
diff --git a/src/common/aes.c b/src/common/aes.c
index 86f3472bfd..49bb54762f 100644
--- a/src/common/aes.c
+++ b/src/common/aes.c
@@ -41,6 +41,7 @@ ENABLE_GCC_WARNING(redundant-decls)
 #include "util.h"
 #include "torlog.h"
 #include "di_ops.h"
+#include "crypto_util.h"
 
 #ifdef ANDROID
 /* Android's OpenSSL seems to have removed all of its Engine support. */
@@ -407,4 +408,3 @@ aes_set_iv(aes_cnt_cipher_t *cipher, const uint8_t *iv)
 }
 
 #endif /* defined(USE_EVP_AES_CTR) */
-