diff --git a/libaaruformat.nuspec b/libaaruformat.nuspec
index 6a5480d..f5656f8 100644
--- a/libaaruformat.nuspec
+++ b/libaaruformat.nuspec
@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
     <metadata>
         <id>libaaruformat</id>
-        <version>1.0.0-alpha.36</version>
+        <version>1.0.0-alpha.37</version>
         <description>Library for management of AaruFormat images.</description>
         <authors>claunia</authors>
         <projectUrl>https://github.com/aaru-dps/libaaruformat</projectUrl>
diff --git a/src/erasure.c b/src/erasure.c
index dd689b3..e91e009 100644
--- a/src/erasure.c
+++ b/src/erasure.c
@@ -96,11 +96,14 @@ AARU_EXPORT int32_t AARU_CALL aaruf_set_erasure_coding(void *context, uint8_t al
 
     /* Compute data shard size: max possible on-disk block size.
      * = sizeof(BlockHeader) + LZMA_PROPERTIES_LENGTH + (1 << dataShift) * sectorSize
-     * This is the worst case: uncompressed block + LZMA properties header. */
+     * This is the worst case: uncompressed block + LZMA properties header.
+     * Use image_info.SectorSize (set by aaruf_create) since current_block_header.sectorSize
+     * may not be set yet if called before the first write. */
     uint32_t sectors_per_block = 1U << ctx->user_data_ddt_header.dataShift;
-    uint32_t max_payload       = sectors_per_block * ctx->current_block_header.sectorSize;
-    if(max_payload == 0) max_payload = sectors_per_block * 512; /* fallback if sectorSize not yet set */
-    uint32_t shard_size = (uint32_t)sizeof(BlockHeader) + LZMA_PROPERTIES_LENGTH + max_payload;
+    uint32_t sector_size       = ctx->image_info.SectorSize;
+    if(sector_size == 0) sector_size = 512;
+    uint32_t max_payload = sectors_per_block * sector_size;
+    uint32_t shard_size  = (uint32_t)sizeof(BlockHeader) + LZMA_PROPERTIES_LENGTH + max_payload;
 
     /* Create RS codec */
     rs_context *rs = rs_create(K, M);
diff --git a/tests/erasure_coding.cpp b/tests/erasure_coding.cpp
index f52d5c7..8d6f79a 100644
--- a/tests/erasure_coding.cpp
+++ b/tests/erasure_coding.cpp
@@ -385,3 +385,19 @@ TEST_F(ErasureCodingTest, BackupHeaderRecovery)
     ASSERT_TRUE(success) << "Backup header recovery failed — could not open/read corrupted image";
     EXPECT_EQ(read_crc, golden_crc) << "CRC mismatch after backup header recovery";
 }
+
+/**
+ * @test Create EC image from a CD image (2048-byte sectors) to exercise non-512 sector sizes.
+ * This catches the shard_size miscalculation that used current_block_header.sectorSize (0)
+ * instead of image_info.SectorSize, causing heap buffer overflow on CD images.
+ */
+TEST_F(ErasureCodingTest, CDSectorSizeImage)
+{
+    uint64_t golden_crc = 0;
+    ASSERT_TRUE(create_ec_image("data/cdmode1.aif", "ec_test_output.aif", 4, 2, &golden_crc));
+
+    bool success = false;
+    uint64_t read_crc = compute_image_crc("ec_test_output.aif", &success);
+    ASSERT_TRUE(success) << "Failed to read all sectors from CD EC image";
+    EXPECT_EQ(read_crc, golden_crc) << "CRC mismatch on CD EC image";
+}