diff --git a/src/multiboot2/is_valid.c b/src/multiboot2/is_valid.c
index b26476f..52fbf01 100644
--- a/src/multiboot2/is_valid.c
+++ b/src/multiboot2/is_valid.c
@@ -229,6 +229,7 @@ unsigned char KernAux_Multiboot2_Tag_MemoryMap_is_valid(
     return (
         tag->base.type == KERNAUX_MULTIBOOT2_TAGTYPE_MEMORY_MAP &&
         tag->base.size >= 16 &&
+        tag->entry_size > 0 &&
         tag->entry_size % 8 == 0 &&
         (tag->base.size - 16) % tag->entry_size == 0
     );
diff --git a/tests/test_multiboot2_validation.c b/tests/test_multiboot2_validation.c
index 673aa5c..864479d 100644
--- a/tests/test_multiboot2_validation.c
+++ b/tests/test_multiboot2_validation.c
@@ -421,6 +421,16 @@ static const struct {
     },
 };
 
+static const struct KernAux_Multiboot2_Tag_MemoryMap
+tag_memory_map_with_empty_data_invalid_entry_size_zero = {
+    .base = {
+        .type = KERNAUX_MULTIBOOT2_TAGTYPE_MEMORY_MAP,
+        .size = 16,
+    },
+    .entry_size = 0,
+    .entry_version = 0,
+};
+
 static const struct KernAux_Multiboot2_Tag_MemoryMap
 tag_memory_map_with_empty_data_invalid_entry_size_not_mul8 = {
     .base = {
@@ -938,6 +948,10 @@ int main()
         &tag_memory_map_with_some_large_data_items_invalid_size.tag.base
     ));
 
+    assert(!KernAux_Multiboot2_TagBase_is_valid(
+        &tag_memory_map_with_empty_data_invalid_entry_size_zero.base
+    ));
+
     assert(!KernAux_Multiboot2_TagBase_is_valid(
         &tag_memory_map_with_empty_data_invalid_entry_size_not_mul8.base
     ));
@@ -1090,6 +1104,10 @@ int main()
         &tag_memory_map_with_some_large_data_items_invalid_size.tag
     ));
 
+    assert(!KernAux_Multiboot2_Tag_MemoryMap_is_valid(
+        &tag_memory_map_with_empty_data_invalid_entry_size_zero
+    ));
+
     assert(!KernAux_Multiboot2_Tag_MemoryMap_is_valid(
         &tag_memory_map_with_empty_data_invalid_entry_size_not_mul8
     ));