diff --git a/src/lib/OpenEXRCore/decoding.c b/src/lib/OpenEXRCore/decoding.c
index d92cab1f4..d3bc438ba 100644
--- a/src/lib/OpenEXRCore/decoding.c
+++ b/src/lib/OpenEXRCore/decoding.c
@@ -590,7 +590,25 @@ exr_decoding_run (
         (part->storage_mode == EXR_STORAGE_DEEP_SCANLINE ||
          part->storage_mode == EXR_STORAGE_DEEP_TILED))
     {
-        if (part->comp_type == EXR_COMPRESSION_NONE &&
+        if (part->comp_type != EXR_COMPRESSION_NONE &&
+            decode->packed_sample_count_table == NULL &&
+            decode->sample_count_table != NULL)
+        {
+            /* A compressed deep chunk declared a zero-length (absent)
+             * packed sample-count table, so decompress_data() above was
+             * never invoked and decode->sample_count_table, which was
+             * allocated to hold the full decompressed table, was left
+             * uninitialized. Treat an absent table as all-zero sample
+             * counts instead of reading uninitialized heap memory in
+             * unpack_sample_table().
+             */
+            memset (
+                decode->sample_count_table,
+                0,
+                decode->sample_count_alloc_size);
+        }
+        else if (
+            part->comp_type == EXR_COMPRESSION_NONE &&
             decode->sample_count_table != decode->packed_sample_count_table)
         {
             /* Check that uncompressed data can be copied in safely.