diff --git a/src/tiffcomposite_int.cpp b/src/tiffcomposite_int.cpp
index ba24287246..0b34a56d4d 100644
--- a/src/tiffcomposite_int.cpp
+++ b/src/tiffcomposite_int.cpp
@@ -1025,9 +1025,16 @@ namespace Exiv2 {
         if (!mn_) {
             return TiffEntryBase::doCount();
         }
+#ifndef SUPPRESS_WARNINGS
         // Count of IFD makernote in tag Exif.Photo.MakerNote is the size of the
         // Makernote in bytes
-        assert(tiffType() == ttUndefined || tiffType() == ttUnsignedByte || tiffType() == ttSignedByte);
+        if (tiffType() != ttUndefined && tiffType() != ttUnsignedByte && tiffType() != ttSignedByte) {
+            EXV_ERROR << "Makernote entry 0x" << std::setw(4)
+                      << std::setfill('0') << std::hex << tag()
+                      << " has incorrect Exif (TIFF) type " << std::dec << tiffType()
+                      << ". (Expected signed or unsigned byte.)\n";
+        }
+#endif
         return mn_->size();
     }
 
diff --git a/test/data/issue_1833_poc.jpg b/test/data/issue_1833_poc.jpg
new file mode 100644
index 0000000000..c9800ceeef
Binary files /dev/null and b/test/data/issue_1833_poc.jpg differ
diff --git a/tests/bugfixes/github/test_issue_1833.py b/tests/bugfixes/github/test_issue_1833.py
new file mode 100644
index 0000000000..5508e08f0e
--- /dev/null
+++ b/tests/bugfixes/github/test_issue_1833.py
@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+from system_tests import CaseMeta, path, check_no_ASAN_UBSAN_errors
+
+class TiffMnEntryDoCountInvalidTiffType(metaclass=CaseMeta):
+    """
+    Test for the bug described in:
+    https://github.com/Exiv2/exiv2/issues/1833
+    """
+    url = "https://github.com/Exiv2/exiv2/issues/1833"
+
+    filename = path("$data_path/issue_1833_poc.jpg")
+    commands = ["$exiv2 -pS $filename"]
+    stderr = [""]
+    retval = [0]
+
+    compare_stdout = check_no_ASAN_UBSAN_errors