diff --git a/src/efivarfs.c b/src/efivarfs.c
index d4cee453..3ab73d1e 100644
--- a/src/efivarfs.c
+++ b/src/efivarfs.c
@@ -324,7 +324,7 @@ efivarfs_del_variable(efi_guid_t guid, const char *name)
 }
 
 static int
-efivarfs_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
+efivarfs_set_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 		      size_t data_size, uint32_t attributes, mode_t mode)
 {
 	char *path;
@@ -471,7 +471,7 @@ efivarfs_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
 }
 
 static int
-efivarfs_append_variable(efi_guid_t guid, const char *name, uint8_t *data,
+efivarfs_append_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 	size_t data_size, uint32_t attributes)
 {
 	int rc;
diff --git a/src/generics.h b/src/generics.h
index 06cf64cd..26377d94 100644
--- a/src/generics.h
+++ b/src/generics.h
@@ -119,7 +119,7 @@ close_dir(void)
  * -- pjones */
 static int UNUSED FLATTEN
 generic_append_variable(efi_guid_t guid, const char *name,
-		       uint8_t *new_data, size_t new_data_size,
+		       const uint8_t *new_data, size_t new_data_size,
 		       uint32_t new_attributes)
 {
 	int rc;
@@ -157,10 +157,8 @@ generic_append_variable(efi_guid_t guid, const char *name,
 		free(d);
 		free(data);
 	} else if (rc < 0 && errno == ENOENT) {
-		data = new_data;
-		data_size = new_data_size;
 		attributes = new_attributes & ~EFI_VARIABLE_APPEND_WRITE;
-		rc = efi_set_variable(guid, name, data, data_size,
+		rc = efi_set_variable(guid, name, new_data, new_data_size,
 				      attributes, 0600);
 	}
 	if (rc < 0)
diff --git a/src/include/efivar/efivar.h b/src/include/efivar/efivar.h
index 1ec9f5a6..b9b265b6 100644
--- a/src/include/efivar/efivar.h
+++ b/src/include/efivar/efivar.h
@@ -45,11 +45,11 @@ extern int efi_get_variable(efi_guid_t guid, const char *name, uint8_t **data,
 extern int efi_del_variable(efi_guid_t guid, const char *name)
 				__attribute__((__nonnull__ (2)));
 extern int efi_set_variable(efi_guid_t guid, const char *name,
-			    uint8_t *data, size_t data_size,
+			    const uint8_t *data, size_t data_size,
 			    uint32_t attributes, mode_t mode)
 				__attribute__((__nonnull__ (2, 3)));
 extern int efi_append_variable(efi_guid_t guid, const char *name,
-			       uint8_t *data, size_t data_size,
+			       const uint8_t *data, size_t data_size,
 			       uint32_t attributes)
 			      __attribute__((__nonnull__ (2, 3)));
 extern int efi_get_next_variable_name(efi_guid_t **guid, char **name)
diff --git a/src/lib.c b/src/lib.c
index 1592cdf9..c17a54d3 100644
--- a/src/lib.c
+++ b/src/lib.c
@@ -30,7 +30,7 @@ struct efi_var_operations *ops = NULL;
 
 VERSION(_efi_set_variable, _efi_set_variable@libefivar.so.0)
 int NONNULL(2, 3) PUBLIC
-_efi_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
+_efi_set_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 		  size_t data_size, uint32_t attributes)
 {
 	int rc;
@@ -47,7 +47,7 @@ _efi_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
 
 VERSION(_efi_set_variable_variadic, efi_set_variable@libefivar.so.0)
 int NONNULL(2, 3) PUBLIC
-_efi_set_variable_variadic(efi_guid_t guid, const char *name, uint8_t *data,
+_efi_set_variable_variadic(efi_guid_t guid, const char *name, const uint8_t *data,
 			   size_t data_size, uint32_t attributes, ...)
 {
 	int rc;
@@ -64,7 +64,7 @@ _efi_set_variable_variadic(efi_guid_t guid, const char *name, uint8_t *data,
 
 VERSION(_efi_set_variable_mode,efi_set_variable@@LIBEFIVAR_0.24)
 int NONNULL(2, 3) PUBLIC
-_efi_set_variable_mode(efi_guid_t guid, const char *name, uint8_t *data,
+_efi_set_variable_mode(efi_guid_t guid, const char *name, const uint8_t *data,
 		       size_t data_size, uint32_t attributes, mode_t mode)
 {
 	int rc;
@@ -82,12 +82,12 @@ _efi_set_variable_mode(efi_guid_t guid, const char *name, uint8_t *data,
 }
 
 int NONNULL(2, 3) PUBLIC
-efi_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
+efi_set_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 		 size_t data_size, uint32_t attributes, mode_t mode)
 	ALIAS(_efi_set_variable_mode);
 
 int NONNULL(2, 3) PUBLIC
-efi_append_variable(efi_guid_t guid, const char *name, uint8_t *data,
+efi_append_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 			size_t data_size, uint32_t attributes)
 {
 	int rc;
diff --git a/src/lib.h b/src/lib.h
index 82fe2933..75d20788 100644
--- a/src/lib.h
+++ b/src/lib.h
@@ -26,7 +26,7 @@ struct efi_variable {
 struct efi_var_operations {
 	char name[NAME_MAX];
 	int (*probe)(void);
-	int (*set_variable)(efi_guid_t guid, const char *name, uint8_t *data,
+	int (*set_variable)(efi_guid_t guid, const char *name, const uint8_t *data,
 			    size_t data_size, uint32_t attributes, mode_t mode);
 	int (*del_variable)(efi_guid_t guid, const char *name);
 	int (*get_variable)(efi_guid_t guid, const char *name, uint8_t **data,
@@ -37,7 +37,7 @@ struct efi_var_operations {
 				 size_t *size);
 	int (*get_next_variable_name)(efi_guid_t **guid, char **name);
 	int (*append_variable)(efi_guid_t guid, const char *name,
-			       uint8_t *data, size_t data_size,
+			       const uint8_t *data, size_t data_size,
 			       uint32_t attributes);
 	int (*chmod_variable)(efi_guid_t guid, const char *name, mode_t mode);
 };
diff --git a/src/vars.c b/src/vars.c
index ea37f85f..1cd23d27 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -511,7 +511,7 @@ vars_chmod_variable(efi_guid_t guid, const char *name, mode_t mode)
 }
 
 static int
-vars_set_variable(efi_guid_t guid, const char *name, uint8_t *data,
+vars_set_variable(efi_guid_t guid, const char *name, const uint8_t *data,
 		 size_t data_size, uint32_t attributes, mode_t mode)
 {
 	int errno_value;