diff --git a/src/miniz.h b/src/miniz.h
index 94afbd19..2f9ee3bd 100644
--- a/src/miniz.h
+++ b/src/miniz.h
@@ -4620,6 +4620,12 @@ tinfl_status tinfl_decompress(tinfl_decompressor *r,
             bit_buf >>= code_len;
             num_bits -= code_len;
 
+            /* assert(sym2 != 0 && counter != 0); */
+            if (sym2 == 0 && counter == 0)
+            {
+                TINFL_CR_RETURN_FOREVER(40, TINFL_STATUS_FAILED);
+            }
+
             pOut_buf_cur[0] = (mz_uint8)counter;
             if (sym2 & 256) {
               pOut_buf_cur++;