diff --git a/rhizome_bundle.c b/rhizome_bundle.c
index 1ed8c0e2..5120b2a9 100644
--- a/rhizome_bundle.c
+++ b/rhizome_bundle.c
@@ -360,6 +360,7 @@ int rhizome_hash_file(rhizome_manifest *m, const char *filename, char *hash_out)
   if (m && m->payloadEncryption) 
     return WHY("Encryption of payloads not implemented");
 
+  size_t filesize = 0;
   SHA512_CTX context;
   SHA512_Init(&context);
   if (filename[0]) {
@@ -378,11 +379,16 @@ int rhizome_hash_file(rhizome_manifest *m, const char *filename, char *hash_out)
       }
       if (r > 0)
 	SHA512_Update(&context, buffer, r);
+      filesize += r;
     }
     fclose(f);
   }
   SHA512_End(&context, (char *)hash_out);
-  str_toupper_inplace(hash_out);
+  // Empty files (including null filename) have no hash.
+  if (filesize > 0)
+    str_toupper_inplace(hash_out);
+  else
+    hash_out[0] = '\0';
   return 0;
 }
 
diff --git a/testdefs_rhizome.sh b/testdefs_rhizome.sh
index 958b06fd..3ac85ec0 100644
--- a/testdefs_rhizome.sh
+++ b/testdefs_rhizome.sh
@@ -274,15 +274,19 @@ extract_manifest_crypt() {
 }
 
 compute_filehash() {
-   local _var="$1"
+   local _filehashvar="$1"
    local _file="$2"
-   local _filesize="$3"
-   local _hash=$($servald rhizome hash file "$_file") || error "$servald failed to compute file hash"
-   [ -z "${_hash//[0-9a-fA-F]/}" ] || error "file hash contains non-hex: $_hash"
-   [ "${#_hash}" -eq 128 ] || error "file hash incorrect length: $_hash"
-   local _size=$(( $(cat "$filename" | wc -c) + 0 ))
-   [ -n "$_var" ] && eval $_var="\$_hash"
-   [ -n "$_filesize" ] && eval $_filesize="\$_size"
+   local _filesizevar="$3"
+   local _hash=
+   local _size=0
+   if [ -s "$_file" ]; then
+      local _hash=$($servald rhizome hash file "$_file") || error "$servald failed to compute file hash"
+      [ -z "${_hash//[0-9a-fA-F]/}" ] || error "file hash contains non-hex: $_hash"
+      [ "${#_hash}" -eq 128 ] || error "file hash incorrect length: $_hash"
+      local _size=$(( $(cat "$filename" | wc -c) + 0 ))
+   fi
+   [ -n "$_filehashvar" ] && eval $_filehashvar="\$_hash"
+   [ -n "$_filesizevar" ] && eval $_filesizevar="\$_size"
 }
 
 rhizome_http_server_started() {