diff --git a/docs/spec/blocks/datastream_payload.adoc b/docs/spec/blocks/datastream_payload.adoc
index c8767c1..2cc138c 100644
--- a/docs/spec/blocks/datastream_payload.adoc
+++ b/docs/spec/blocks/datastream_payload.adoc
@@ -19,6 +19,7 @@ For other data types, the payload layout is specific to the data type.
 typedef struct DataStreamPayloadHeader
 {
     uint32_t identifier;  ///< Block identifier, must be BlockType::DataStreamPayloadBlock (0x4C505344).
+    uint16_t dataType;    ///< Data type classification (value from DataType), e.g., FluxData or BitstreamData.
     uint16_t compression; ///< Compression type (0 = None, 1 = Lzma).
     uint32_t cmpLength;   ///< Compressed length in bytes (includes LZMA properties if compressed).
     uint32_t length;      ///< Uncompressed length in bytes.
@@ -40,6 +41,11 @@ typedef struct DataStreamPayloadHeader
 |identifier
 |The data stream payload block identifier, always `DSPL` (`0x4C505344`)
 
+|uint16_t
+|2 bytes
+|dataType
+|The data type contained in this block (value from DataType), e.g., FluxData or BitstreamData. See Annex B.
+
 |uint16_t
 |2 bytes
 |compression
diff --git a/include/aaruformat/structs/flux.h b/include/aaruformat/structs/flux.h
index 61befd9..f8f8f08 100644
--- a/include/aaruformat/structs/flux.h
+++ b/include/aaruformat/structs/flux.h
@@ -201,6 +201,12 @@ typedef struct FluxCaptureMapEntry FluxCaptureMapEntry;
  * may be compressed using LZMA compression. Currently used for flux capture data, but
  * can be used for other data streams such as bitstreams or PNG data.
  *
+ * **Data Type:**
+ * The dataType field identifies the type of data stored in the payload. Common values include:
+ * - FluxData: Flux capture data (data and index buffers)
+ * - BitstreamData: Bitstream data
+ * This field enables the block to be self-describing and allows validation of the payload content.
+ *
  * **Compression:**
  * The compression field indicates whether the payload is compressed:
  * - 0 (None): Payload is stored uncompressed
@@ -226,6 +232,7 @@ typedef struct FluxCaptureMapEntry FluxCaptureMapEntry;
 typedef struct DataStreamPayloadHeader
 {
     uint32_t identifier;   ///< Block identifier, must be BlockType::DataStreamPayloadBlock (0x4C505344, "DSPL").
+    uint16_t dataType;     ///< Data type classification (value from \ref DataType), e.g., FluxData or BitstreamData.
     uint16_t compression;  ///< Compression type: 0 = None, 1 = Lzma.
     uint32_t cmpLength;    ///< Compressed length in bytes (includes LZMA properties if compression = Lzma).
     uint32_t length;       ///< Uncompressed length in bytes.
diff --git a/src/blocks/flux.c b/src/blocks/flux.c
index 7a7bfec..23470db 100644
--- a/src/blocks/flux.c
+++ b/src/blocks/flux.c
@@ -832,6 +832,14 @@ static int32_t read_flux_payload_header(const aaruformat_context *ctx, uint64_t
         return AARUF_ERROR_CANNOT_READ_BLOCK;
     }
 
+    if(header->dataType != FluxData)
+    {
+        FATAL("Incorrect data type %u for flux payload at offset %" PRIu64 " (expected FluxData)", header->dataType,
+              payload_offset);
+        TRACE("Exiting read_flux_payload_header() = AARUF_ERROR_CANNOT_READ_BLOCK\n");
+        return AARUF_ERROR_CANNOT_READ_BLOCK;
+    }
+
     return AARUF_STATUS_OK;
 }
 
diff --git a/src/close.c b/src/close.c
index 958662a..5d15f30 100644
--- a/src/close.c
+++ b/src/close.c
@@ -4468,6 +4468,7 @@ static int32_t write_flux_capture_payload(aaruformat_context *ctx, FluxCaptureRe
 
     DataStreamPayloadHeader payload_header = {0};
     payload_header.identifier              = DataStreamPayloadBlock;
+    payload_header.dataType                = FluxData;
     payload_header.compression             = (uint16_t)compression;
     payload_header.cmpLength               = cmp_length;
     payload_header.length                  = (uint32_t)raw_length;
diff --git a/templates/aaruformat.hexpat b/templates/aaruformat.hexpat
index f59fe65..adffe1d 100644
--- a/templates/aaruformat.hexpat
+++ b/templates/aaruformat.hexpat
@@ -1164,6 +1164,7 @@ struct FluxDataBlock
 struct DataStreamPayloadHeader
 {
     BlockType       identifier;
+    u16             dataType;
     u16             compression;
     u32             cmpLength;
     u32             length;