diff --git a/go/heif/heif.go b/go/heif/heif.go
index 85706b84cb..55b638706c 100644
--- a/go/heif/heif.go
+++ b/go/heif/heif.go
@@ -339,6 +339,8 @@ const (
 
 	SuberrorUnsupportedGenericCompressionMethod = C.heif_suberror_Unsupported_generic_compression_method
 
+	SuberrorUnsupportedEssentialProperty = C.heif_suberror_Unsupported_essential_property
+
 	// The conversion of the source image to the requested chroma / colorspace is not supported.
 	SuberrorUnsupportedColorConversion = C.heif_suberror_Unsupported_color_conversion
 
diff --git a/libheif/api/libheif/heif.h b/libheif/api/libheif/heif.h
index 97d2396f9a..6753c0054b 100644
--- a/libheif/api/libheif/heif.h
+++ b/libheif/api/libheif/heif.h
@@ -312,6 +312,8 @@ enum heif_suberror_code
   // Generically compressed data used an unsupported compression method
   heif_suberror_Unsupported_generic_compression_method = 3006,
 
+  heif_suberror_Unsupported_essential_property = 3007,
+
   // --- Encoder_plugin_error ---
 
   heif_suberror_Unsupported_bit_depth = 4000,
diff --git a/libheif/api/libheif/heif_emscripten.h b/libheif/api/libheif/heif_emscripten.h
index 5b015f1288..46c0c8c7dc 100644
--- a/libheif/api/libheif/heif_emscripten.h
+++ b/libheif/api/libheif/heif_emscripten.h
@@ -389,6 +389,7 @@ EMSCRIPTEN_BINDINGS(libheif) {
     .value("heif_suberror_Unsupported_image_type", heif_suberror_Unsupported_image_type)
     .value("heif_suberror_Unsupported_data_version", heif_suberror_Unsupported_data_version)
     .value("heif_suberror_Unsupported_generic_compression_method", heif_suberror_Unsupported_generic_compression_method)
+    .value("heif_suberror_Unsupported_essential_property", heif_suberror_Unsupported_essential_property)
     .value("heif_suberror_Unsupported_color_conversion", heif_suberror_Unsupported_color_conversion)
     .value("heif_suberror_Unsupported_item_construction_method", heif_suberror_Unsupported_item_construction_method)
     .value("heif_suberror_Unsupported_header_compression_method", heif_suberror_Unsupported_header_compression_method)
diff --git a/libheif/box.cc b/libheif/box.cc
index 858ce43d42..8599519750 100644
--- a/libheif/box.cc
+++ b/libheif/box.cc
@@ -2471,9 +2471,9 @@ bool Box_ipco::is_property_essential_for_item(heif_item_id itemId,
 {
   // find property index
 
-  for (int i=0;i<(int)m_children.size();i++) {
+  for (int i = 0; i < (int) m_children.size(); i++) {
     if (m_children[i] == property) {
-      return ipma->is_property_essential_for_item(itemId, i);
+      return ipma->is_property_essential_for_item(itemId, i + 1);
     }
   }
 
diff --git a/libheif/context.cc b/libheif/context.cc
index 1a97821f0e..a3afac446f 100644
--- a/libheif/context.cc
+++ b/libheif/context.cc
@@ -327,7 +327,7 @@ Error HeifContext::interpret_heif_file()
   }
 
 
-  // --- read through properties for each image and extract image resolutions
+  // --- process image properties
 
   for (auto& pair : m_all_images) {
     auto& image = pair.second;
@@ -339,6 +339,23 @@ Error HeifContext::interpret_heif_file()
       return err;
     }
 
+
+    // --- are there any 'essential' properties that we did not parse?
+
+
+    for (const auto& prop : properties) {
+      if (std::dynamic_pointer_cast<Box_other>(prop) &&
+          get_heif_file()->get_ipco_box()->is_property_essential_for_item(pair.first, prop, get_heif_file()->get_ipma_box())) {
+
+        std::stringstream sstr;
+        sstr << "could not parse item property '" << prop->get_type_string() << "'";
+        return {heif_error_Unsupported_feature, heif_suberror_Unsupported_essential_property, sstr.str()};
+      }
+    }
+
+
+    // --- extract image resolution
+
     bool ispe_read = false;
     for (const auto& prop : properties) {
       auto ispe = std::dynamic_pointer_cast<Box_ispe>(prop);
diff --git a/libheif/error.cc b/libheif/error.cc
index 1caa5348fc..caa2bed943 100644
--- a/libheif/error.cc
+++ b/libheif/error.cc
@@ -218,6 +218,8 @@ const char* Error::get_error_string(heif_suberror_code err)
       return "Unsupported header compression method";
     case heif_suberror_Unsupported_generic_compression_method:
       return "Unsupported generic compression method";
+    case heif_suberror_Unsupported_essential_property:
+      return "Unsupported essential item property";
 
       // --- Encoder_plugin_error --