diff --git a/include/kernaux/multiboot2.h b/include/kernaux/multiboot2.h
index a82a5e6..561511f 100644
--- a/include/kernaux/multiboot2.h
+++ b/include/kernaux/multiboot2.h
@@ -19,6 +19,8 @@ extern "C" {
 
 #define KERNAUX_MULTIBOOT2_DATA(ptr) (((uint8_t*)(ptr)) + sizeof(*(ptr)))
 
+#define KERNAUX_MULTIBOOT2_TAG_ALIGN 8
+
 #define KERNAUX_MULTIBOOT2_HTAG_NEXT(tag_base) \
     ((struct KernAux_Multiboot2_HTagBase*)KERNAUX_MULTIBOOT2_TAG_NEXT(tag_base))
 #define KERNAUX_MULTIBOOT2_ITAG_NEXT(tag_base) \
diff --git a/src/multiboot2/header_is_valid.c b/src/multiboot2/header_is_valid.c
index 3f7f14d..b3afef7 100644
--- a/src/multiboot2/header_is_valid.c
+++ b/src/multiboot2/header_is_valid.c
@@ -26,6 +26,10 @@ bool KernAux_Multiboot2_Header_is_valid(
         return false;
     }
 
+    if (multiboot2_header->total_size % KERNAUX_MULTIBOOT2_TAG_ALIGN != 0) {
+        return false;
+    }
+
     if (multiboot2_header->checksum !=
         KERNAUX_MULTIBOOT2_CHECKSUM(
             multiboot2_header->arch,
diff --git a/src/multiboot2/info_is_valid.c b/src/multiboot2/info_is_valid.c
index 64be3bd..36ce1c7 100644
--- a/src/multiboot2/info_is_valid.c
+++ b/src/multiboot2/info_is_valid.c
@@ -18,6 +18,10 @@ bool KernAux_Multiboot2_Info_is_valid(
         return false;
     }
 
+    if (multiboot2_info->total_size % KERNAUX_MULTIBOOT2_TAG_ALIGN != 0) {
+        return false;
+    }
+
     const struct KernAux_Multiboot2_ITagBase *tag_base =
         (struct KernAux_Multiboot2_ITagBase*)
         KERNAUX_MULTIBOOT2_DATA(multiboot2_info);