diff --git a/qrexec-lib/unpack.c b/qrexec-lib/unpack.c
index b3c3f456..3aa363c9 100644
--- a/qrexec-lib/unpack.c
+++ b/qrexec-lib/unpack.c
@@ -204,7 +204,7 @@ void process_one_file_reg(struct file_header *untrusted_hdr,
     const char *last_segment;
     char *path_dup;
 
-    if (!qubes_pure_validate_file_name((uint8_t *)untrusted_name))
+    if (!qubes_pure_validate_file_name((const uint8_t *)untrusted_name))
         do_exit(EILSEQ, untrusted_name); /* FIXME: better error message */
     if ((path_dup = strdup(untrusted_name)) == NULL)
         do_exit(ENOMEM, untrusted_name);
@@ -266,7 +266,7 @@ void process_one_file_dir(struct file_header *untrusted_hdr,
     int safe_dirfd;
     const char *last_segment;
     char *path_dup;
-    if (!qubes_pure_validate_file_name((uint8_t *)untrusted_name))
+    if (!qubes_pure_validate_file_name((const uint8_t *)untrusted_name))
         do_exit(EILSEQ, untrusted_name); /* FIXME: better error message */
     if ((path_dup = strdup(untrusted_name)) == NULL)
         do_exit(ENOMEM, untrusted_name);
@@ -298,7 +298,7 @@ void process_one_file_link(struct file_header *untrusted_hdr,
     const char *last_segment;
     char *path_dup;
     unsigned int filelen;
-    if (!qubes_pure_validate_file_name((uint8_t *)untrusted_name))
+    if (!qubes_pure_validate_file_name((const uint8_t *)untrusted_name))
         do_exit(EILSEQ, untrusted_name); /* FIXME: better error message */
     int safe_dirfd;
     if (untrusted_hdr->filelen > MAX_PATH_LENGTH - 1)
@@ -315,8 +315,8 @@ void process_one_file_link(struct file_header *untrusted_hdr,
      * Ensure that no immediate subdirectory of ~/QubesIncoming/VMNAME
      * may have symlinks that point out of it.
      */
-    if (!qubes_pure_validate_symbolic_link((uint8_t *)untrusted_name,
-                                           (uint8_t *)untrusted_content))
+    if (!qubes_pure_validate_symbolic_link((const uint8_t *)untrusted_name,
+                                           (const uint8_t *)untrusted_content))
         do_exit(EILSEQ, untrusted_content);
 
     if ((path_dup = strdup(untrusted_name)) == NULL)
diff --git a/qrexec-lib/validator-test.c b/qrexec-lib/validator-test.c
index 614ce083..f170bf27 100644
--- a/qrexec-lib/validator-test.c
+++ b/qrexec-lib/validator-test.c
@@ -70,34 +70,34 @@ int main(int argc, char **argv)
 {
     (void)argc;
     (void)argv;
-    assert(qubes_pure_validate_file_name((uint8_t *)u8"simple_safe_filename.txt"));
+    assert(qubes_pure_validate_file_name((const uint8_t *)u8"simple_safe_filename.txt"));
 
     // Directory traversal checks
-    assert(!qubes_pure_validate_file_name((uint8_t *)".."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"../.."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/.."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/../b"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"/"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"//"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"///"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"/a"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"//a"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"///a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)".."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"../.."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/.."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/../b"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"/"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"//"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"///"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"/a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"//a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"///a"));
 
     // No repeated slashes
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a//b"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a//b"));
 
     // No "." as a path component
-    assert(!qubes_pure_validate_file_name((uint8_t *)"."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"./a"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/./a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"./a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/./a"));
 
     // No ".." as a path component
-    assert(!qubes_pure_validate_file_name((uint8_t *)".."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/.."));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"../a"));
-    assert(!qubes_pure_validate_file_name((uint8_t *)"a/../a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)".."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/.."));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"../a"));
+    assert(!qubes_pure_validate_file_name((const uint8_t *)"a/../a"));
 
     // Looks like "." or ".." but is not
     assert(qubes_pure_validate_file_name((const uint8_t *)".a"));