diff --git a/pressure-vessel/supported-architectures.h b/pressure-vessel/supported-architectures.h
index 6d75f45eac7890f116e972cc70e8394cc7a489ce..96f0c0b54f6b5df2ca3926ae963131199371c886 100644
--- a/pressure-vessel/supported-architectures.h
+++ b/pressure-vessel/supported-architectures.h
@@ -31,6 +31,10 @@
 #define PV_N_SUPPORTED_ARCHITECTURES 1
 #endif
 
+/* Currently the 0'th architecture is always the primary one
+ * (x86_64 on x86) */
+#define PV_PRIMARY_ARCHITECTURE 0
+
 #if defined(__i386__) || defined(__x86_64__)
 #define PV_N_SUPPORTED_ARCHITECTURES_AS_EMULATOR_HOST 1 /* AArch64 */
 #else