diff --git a/pkgs/build-support/fetchsvn/nix-prefetch-svn b/pkgs/build-support/fetchsvn/nix-prefetch-svn
index 794061ae4203..879b96f070ef 100755
--- a/pkgs/build-support/fetchsvn/nix-prefetch-svn
+++ b/pkgs/build-support/fetchsvn/nix-prefetch-svn
@@ -42,7 +42,7 @@ if test -z "$finalPath"; then
     mkdir $tmpPath
 
     # Perform the checkout.
-    svn export -r "$rev" "$url" $tmpFile >&2
+    echo p | svn export -r "$rev" "$url" $tmpFile >&2
 
     # Compute the hash.
     hash=$(nix-hash --type $hashType $hashFormat $tmpFile)