diff --git a/programs/fileio.c b/programs/fileio.c
index 55c87313d..cf4ae6dbd 100644
--- a/programs/fileio.c
+++ b/programs/fileio.c
@@ -1070,6 +1070,17 @@ enum {
     FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED = 4
 };
 
+enum {
+    FIO_RUST_COMPRESS_DIAGNOSTIC_OK = 0,
+    FIO_RUST_COMPRESS_DIAGNOSTIC_GZIP_UNSUPPORTED = 1,
+    FIO_RUST_COMPRESS_DIAGNOSTIC_LZMA_UNSUPPORTED = 2,
+    FIO_RUST_COMPRESS_DIAGNOSTIC_LZ4_UNSUPPORTED = 3,
+    FIO_RUST_COMPRESS_DIAGNOSTIC_ZSTD_UNSUPPORTED = 4,
+    FIO_RUST_COMPRESS_DIAGNOSTIC_UNKNOWN = 5
+};
+
+int FIO_rust_compressFilenameDiagnostic(int status);
+
 typedef unsigned long long (*FIO_rust_compress_zstd_fn)(
         void* fCtx, void* prefs, void* ress,
         const char* srcFileName, U64 srcFileSize,
@@ -3005,6 +3016,7 @@ FIO_compressFilename_internal(FIO_ctx_t* const fCtx,
     U64 const fileSize = UTIL_getFileSize(srcFileName);
     FIO_rust_compress_callbacks_t callbacks;
     int status;
+    int diagnostic;
 
     memset(&callbacks, 0, sizeof(callbacks));
     callbacks.opaque = &displayCtx;
@@ -3025,19 +3037,20 @@ FIO_compressFilename_internal(FIO_ctx_t* const fCtx,
         fCtx, prefs, &ress, dstFileName, srcFileName, fileSize,
         compressionLevel, &callbacks);
 
-    switch (status) {
-        case FIO_RUST_COMPRESS_OK:
+    diagnostic = FIO_rust_compressFilenameDiagnostic(status);
+    switch (diagnostic) {
+        case FIO_RUST_COMPRESS_DIAGNOSTIC_OK:
             return 0;
-        case FIO_RUST_COMPRESS_GZIP_UNSUPPORTED:
+        case FIO_RUST_COMPRESS_DIAGNOSTIC_GZIP_UNSUPPORTED:
             EXM_THROW(20, "zstd: %s: file cannot be compressed as gzip (zstd compiled without ZSTD_GZCOMPRESS) -- ignored \n",
                       srcFileName);
-        case FIO_RUST_COMPRESS_LZMA_UNSUPPORTED:
+        case FIO_RUST_COMPRESS_DIAGNOSTIC_LZMA_UNSUPPORTED:
             EXM_THROW(20, "zstd: %s: file cannot be compressed as xz/lzma (zstd compiled without ZSTD_LZMACOMPRESS) -- ignored \n",
                       srcFileName);
-        case FIO_RUST_COMPRESS_LZ4_UNSUPPORTED:
+        case FIO_RUST_COMPRESS_DIAGNOSTIC_LZ4_UNSUPPORTED:
             EXM_THROW(20, "zstd: %s: file cannot be compressed as lz4 (zstd compiled without ZSTD_LZ4COMPRESS) -- ignored \n",
                       srcFileName);
-        case FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED:
+        case FIO_RUST_COMPRESS_DIAGNOSTIC_ZSTD_UNSUPPORTED:
         default:
             assert(status == FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED);
             EXM_THROW(20, "zstd: %s: file cannot be compressed as zstd -- ignored \n",
diff --git a/rust/src/fileio_asyncio.rs b/rust/src/fileio_asyncio.rs
index 726a2becd..225c79e39 100644
--- a/rust/src/fileio_asyncio.rs
+++ b/rust/src/fileio_asyncio.rs
@@ -250,6 +250,27 @@ pub const FIO_RUST_COMPRESS_LZMA_UNSUPPORTED: c_int = 2;
 pub const FIO_RUST_COMPRESS_LZ4_UNSUPPORTED: c_int = 3;
 pub const FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED: c_int = 4;
 
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_OK: c_int = 0;
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_GZIP_UNSUPPORTED: c_int = 1;
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_LZMA_UNSUPPORTED: c_int = 2;
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_LZ4_UNSUPPORTED: c_int = 3;
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_ZSTD_UNSUPPORTED: c_int = 4;
+pub const FIO_RUST_COMPRESS_DIAGNOSTIC_UNKNOWN: c_int = 5;
+
+/// Classifies the aggregate compression-selector result while leaving the
+/// format-specific exception text and fallback assertion in C.
+#[no_mangle]
+pub extern "C" fn FIO_rust_compressFilenameDiagnostic(status: c_int) -> c_int {
+    match status {
+        FIO_RUST_COMPRESS_OK => FIO_RUST_COMPRESS_DIAGNOSTIC_OK,
+        FIO_RUST_COMPRESS_GZIP_UNSUPPORTED => FIO_RUST_COMPRESS_DIAGNOSTIC_GZIP_UNSUPPORTED,
+        FIO_RUST_COMPRESS_LZMA_UNSUPPORTED => FIO_RUST_COMPRESS_DIAGNOSTIC_LZMA_UNSUPPORTED,
+        FIO_RUST_COMPRESS_LZ4_UNSUPPORTED => FIO_RUST_COMPRESS_DIAGNOSTIC_LZ4_UNSUPPORTED,
+        FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED => FIO_RUST_COMPRESS_DIAGNOSTIC_ZSTD_UNSUPPORTED,
+        _ => FIO_RUST_COMPRESS_DIAGNOSTIC_UNKNOWN,
+    }
+}
+
 const FIO_ZSTD_COMPRESSION: c_int = 0;
 const FIO_GZIP_COMPRESSION: c_int = 1;
 const FIO_XZ_COMPRESSION: c_int = 2;
@@ -5438,6 +5459,38 @@ mod tests {
         }
     }
 
+    #[test]
+    fn aggregate_compression_status_diagnostic_preserves_format_mapping() {
+        for (status, diagnostic) in [
+            (FIO_RUST_COMPRESS_OK, FIO_RUST_COMPRESS_DIAGNOSTIC_OK),
+            (
+                FIO_RUST_COMPRESS_GZIP_UNSUPPORTED,
+                FIO_RUST_COMPRESS_DIAGNOSTIC_GZIP_UNSUPPORTED,
+            ),
+            (
+                FIO_RUST_COMPRESS_LZMA_UNSUPPORTED,
+                FIO_RUST_COMPRESS_DIAGNOSTIC_LZMA_UNSUPPORTED,
+            ),
+            (
+                FIO_RUST_COMPRESS_LZ4_UNSUPPORTED,
+                FIO_RUST_COMPRESS_DIAGNOSTIC_LZ4_UNSUPPORTED,
+            ),
+            (
+                FIO_RUST_COMPRESS_ZSTD_UNSUPPORTED,
+                FIO_RUST_COMPRESS_DIAGNOSTIC_ZSTD_UNSUPPORTED,
+            ),
+        ] {
+            assert_eq!(FIO_rust_compressFilenameDiagnostic(status), diagnostic);
+        }
+
+        for status in [-1, 99] {
+            assert_eq!(
+                FIO_rust_compressFilenameDiagnostic(status),
+                FIO_RUST_COMPRESS_DIAGNOSTIC_UNKNOWN
+            );
+        }
+    }
+
     const SOURCE_POLICY_STAT: u8 = 1;
     const SOURCE_POLICY_EXCLUDED: u8 = 2;
     const SOURCE_POLICY_OPEN: u8 = 3;