diff --git a/src/shared/efivars.c b/src/shared/efivars.c
index 23d38fb484..0c7adb30fb 100644
--- a/src/shared/efivars.c
+++ b/src/shared/efivars.c
@@ -40,11 +40,17 @@
 #define END_ENTIRE_DEVICE_PATH_SUBTYPE      0xff
 #define EFI_OS_INDICATIONS_BOOT_TO_FW_UI    0x0000000000000001
 
-struct boot_option {
-        uint32_t attr;
-        uint16_t path_len;
-        uint16_t title[];
-} _packed_;
+#define boot_option__contents {                 \
+        uint32_t attr;                          \
+        uint16_t path_len;                      \
+        uint16_t title[];                       \
+        }
+
+struct boot_option boot_option__contents;
+struct boot_option__packed boot_option__contents _packed_;
+assert_cc(offsetof(struct boot_option, title) == offsetof(struct boot_option__packed, title));
+/* sizeof(struct boot_option) != sizeof(struct boot_option__packed), so
+ * the *size* of the structure should not be used anywhere below. */
 
 struct drive_path {
         uint32_t part_nr;
@@ -354,13 +360,21 @@ int efi_set_variable_string(sd_id128_t vendor, const char *name, const char *v)
         return efi_set_variable(vendor, name, u16, (char16_strlen(u16) + 1) * sizeof(char16_t));
 }
 
-static size_t utf16_size(const uint16_t *s) {
+static ssize_t utf16_size(const uint16_t *s, size_t buf_len_bytes) {
         size_t l = 0;
 
-        while (s[l] > 0)
-                l++;
+        /* Returns the size of the string in bytes without the terminating two zero bytes */
 
-        return (l+1) * sizeof(uint16_t);
+        if (buf_len_bytes % sizeof(uint16_t) != 0)
+                return -EINVAL;
+
+        while (l < buf_len_bytes / sizeof(uint16_t)) {
+                if (s[l] == 0)
+                        return (l + 1) * sizeof(uint16_t);
+                l++;
+        }
+
+        return -EINVAL; /* The terminator was not found */
 }
 
 static void efi_guid_to_id128(const void *guid, sd_id128_t *id128) {
@@ -394,7 +408,7 @@ int efi_get_boot_option(
         _cleanup_free_ uint8_t *buf = NULL;
         size_t l;
         struct boot_option *header;
-        size_t title_size;
+        ssize_t title_size;
         _cleanup_free_ char *s = NULL, *p = NULL;
         sd_id128_t p_uuid = SD_ID128_NULL;
         int r;
@@ -406,13 +420,13 @@ int efi_get_boot_option(
         r = efi_get_variable(EFI_VENDOR_GLOBAL, boot_id, NULL, (void **)&buf, &l);
         if (r < 0)
                 return r;
-        if (l < sizeof(struct boot_option))
+        if (l < offsetof(struct boot_option, title))
                 return -ENOENT;
 
         header = (struct boot_option *)buf;
-        title_size = utf16_size(header->title);
-        if (title_size > l - offsetof(struct boot_option, title))
-                return -EINVAL;
+        title_size = utf16_size(header->title, l - offsetof(struct boot_option, title));
+        if (title_size < 0)
+                return title_size;
 
         if (title) {
                 s = utf16_to_utf8(header->title, title_size);
@@ -541,7 +555,7 @@ int efi_add_boot_option(
         title_len = (strlen(title)+1) * 2;
         path_len = (strlen(path)+1) * 2;
 
-        buf = malloc0(sizeof(struct boot_option) + title_len +
+        buf = malloc0(offsetof(struct boot_option, title) + title_len +
                       sizeof(struct drive_path) +
                       sizeof(struct device_path) + path_len);
         if (!buf)