diff --git a/crypto/modes/cbc.c b/crypto/modes/cbc.c
index ba4805b..f0889ef 100644
--- a/crypto/modes/cbc.c
+++ b/crypto/modes/cbc.c
@@ -121,7 +121,10 @@
 
   assert(in && out && key && ivec);
 
-  if (in != out) {
+  const uintptr_t inptr = (uintptr_t) in;
+  const uintptr_t outptr = (uintptr_t) out;
+
+  if ((inptr >= 32 && outptr <= inptr - 32) || inptr < outptr) {
     const uint8_t *iv = ivec;
 
     if (STRICT_ALIGNMENT &&