diff --git a/comm_b.c b/comm_b.c
index 19373c3..2cc2656 100644
--- a/comm_b.c
+++ b/comm_b.c
@@ -783,7 +783,7 @@ static int decodeBDS44(struct modesMessage *mm, bool store)
     unsigned humidity_valid = getbit(msg, 50);
     unsigned humidity_raw = getbits(msg, 51, 56);
 
-    if (source == MRAR_SOURCE_INVALID || source > 5)
+    if (source == MRAR_SOURCE_INVALID || source >= MRAR_SOURCE_RESERVED)
         return 0; // invalid or reserved source
 
     if (!wind_valid || !sat_valid)
diff --git a/dump1090.h b/dump1090.h
index 96262c4..31d48e2 100644
--- a/dump1090.h
+++ b/dump1090.h
@@ -244,7 +244,8 @@ typedef enum {
    MRAR_SOURCE_INS = 1,
    MRAR_SOURCE_GNSS = 2,
    MRAR_SOURCE_DMEDME = 3,
-   MRAR_SOURCE_VORDME = 4
+   MRAR_SOURCE_VORDME = 4,
+   MRAR_SOURCE_RESERVED = 5
 } mrar_source_t;
 
 // BDS4,4 and BDS4,5 hazard reports