diff --git a/nextflow.config b/nextflow.config
index 9f3b103..588c0cf 100644
--- a/nextflow.config
+++ b/nextflow.config
@@ -158,7 +158,8 @@ if (!params.igenomes_ignore) {
 // See https://apeltzer.github.io/post/03-julia-lang-nextflow/ for details on that. Once we have a common agreement on where to keep Julia packages, this is adjustable.
 
 env {
-    PYTHONNOUSERSITE = 1
+    PYTHONNOUSERSITE = '1'
+    PYTHONUTF8       = '1'  // MetaPhlAn3 may fail with a UnicodeDecodeError if the locale is not set appropriately.
     R_PROFILE_USER   = "/.Rprofile"
     R_ENVIRON_USER   = "/.Renviron"
     JULIA_DEPOT_PATH = "/usr/local/share/julia"