diff --git a/openrtx/src/protocols/M17/M17Callsign.cpp b/openrtx/src/protocols/M17/M17Callsign.cpp
index eeb91b02..d636b314 100644
--- a/openrtx/src/protocols/M17/M17Callsign.cpp
+++ b/openrtx/src/protocols/M17/M17Callsign.cpp
@@ -86,7 +86,7 @@ std::string M17::decode_callsign(const call_t& encodedCall)
      * Address is not broadcast, decode it.
      * TODO: current implementation works only on little endian architectures.
      */
-    static const char charMap[] = "xABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/.";
+    static const char charMap[] = " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/.";
 
     uint64_t encoded = 0;
     auto p = reinterpret_cast<uint8_t*>(&encoded);