diff --git a/client/src/cmdlfio.c b/client/src/cmdlfio.c
index bb05af40f..23172bcae 100644
--- a/client/src/cmdlfio.c
+++ b/client/src/cmdlfio.c
@@ -316,6 +316,9 @@ static int CmdIOProxClone(const char *Cmd) {
 
     // EM4305
     if (em) {
+        // TODO: it seems an EM4305 tag supporting FSK still runs at RF/50 even if configured at RF/64
+        // lf em 4x05 info <> lf read ; data detectclock --fs
+        // So, it seems cloning ioProx on EM4305 is not possible...
         blocks[0] = EM4305_IOPROX_CONFIG_BLOCK;
         snprintf(cardtype, sizeof(cardtype), "EM4305/4469");
     }
@@ -323,6 +326,14 @@ static int CmdIOProxClone(const char *Cmd) {
     blocks[1] = bytebits_to_byte(bits, 32);
     blocks[2] = bytebits_to_byte(bits + 32, 32);
 
+    // EM4305
+    if (em) {
+        // invert FSK data
+        for (uint8_t i = 1; i < ARRAYLEN(blocks); i++) {
+                blocks[i] = blocks[i] ^ 0xFFFFFFFF;
+        }
+    }
+
     PrintAndLogEx(INFO, "Preparing to clone ioProx to " _YELLOW_("%s") " with Version: " _GREEN_("%u") " FC: " _GREEN_("%u (0x%02x)") " CN: " _GREEN_("%u")
                   , cardtype
                   , version