diff --git a/library/aes.c b/library/aes.c
index 1e1039b..63b36c5 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -52,10 +52,15 @@
 #error "MBEDTLS_AES_USE_HARDWARE_ONLY defined, but not all prerequisites"
 #endif
 
-#if defined(MBEDTLS_PADLOCK_C) && \
-    (!defined(MBEDTLS_HAVE_ASM) || defined(MBEDTLS_AES_USE_HARDWARE_ONLY))
+#if defined(MBEDTLS_PADLOCK_C)
+#if !defined(MBEDTLS_HAVE_ASM)
 #error "MBEDTLS_PADLOCK_C defined, but not all prerequisites"
 #endif
+#if defined(MBEDTLS_AES_USE_HARDWARE_ONLY)
+#error "MBEDTLS_AES_USE_HARDWARE_ONLY cannot be defined when " \
+    "MBEDTLS_PADLOCK_C is set"
+#endif
+#endif
 #endif
 
 #if defined(MBEDTLS_PADLOCK_C)