diff --git a/minix/lib/libexec/exec_elf.c b/minix/lib/libexec/exec_elf.c
index f6d8d21cd..fca784aeb 100644
--- a/minix/lib/libexec/exec_elf.c
+++ b/minix/lib/libexec/exec_elf.c
@@ -58,7 +58,8 @@ static int elf_ph_sane(Elf_Phdr *phdr)
 static int elf_unpack(char *exec_hdr,
 	int hdr_len, Elf_Ehdr **hdr, Elf_Phdr **phdr)
 {
-  assert(hdr_len >= sizeof(Elf_Ehdr));
+  if(hdr_len < sizeof(Elf_Ehdr))
+	return ENOEXEC;
 
   *hdr = (Elf_Ehdr *) exec_hdr;
   if(!elf_sane(*hdr)) {