diff --git a/bin/panama b/bin/panama
index 6db8338..0779d9f 100755
--- a/bin/panama
+++ b/bin/panama
@@ -451,11 +451,16 @@ CONTRACT_CAPABILITIES=(hermetic live-host live-compositor live-desktop network p
 
 contract_paths() {
   local candidate
+  # The manifest is kept in byte order, so both the discovery sort and the
+  # comparison below have to be byte order too. A UTF-8 collation folds the
+  # punctuation away -- `calendar_agenda_bridge_test.py` sorts before
+  # `calendar-agenda-helper-contract` under en_US and after it under C -- and
+  # a gate that passes or fails on the machine's LANG is not a gate.
   while IFS= read -r candidate; do
     [[ -x "$candidate" || "$candidate" == *_test.py ]] || continue
     printf 'tests/%s\n' "${candidate#"$PANAMA_DIR/tests/"}"
   done < <(find "$PANAMA_DIR/tests" -type f \
-    -not -path '*/fixtures/*' -not -path '*__pycache__*' | sort)
+    -not -path '*/fixtures/*' -not -path '*__pycache__*' | LC_ALL=C sort)
 }
 
 contract_manifest_entries() {
@@ -478,6 +483,8 @@ validate_contract_manifest() {
   require_contract_manifest || return 1
 
   local manifest="$PANAMA_DIR/$CONTRACT_MANIFEST"
+  # Byte order, for the same reason contract_paths sorts in it.
+  local LC_ALL=C
   local line capabilities path extra previous_comment="" previous_was_comment=0
   local previous_path="" capability discovered
   local -a capability_list=() findings=()
diff --git a/tests/setup/contract-manifest-contract b/tests/setup/contract-manifest-contract
index eb26af0..a4a5755 100755
--- a/tests/setup/contract-manifest-contract
+++ b/tests/setup/contract-manifest-contract
@@ -11,16 +11,22 @@ manifest="$repo_dir/tests/contracts.manifest"
 
 discover_contracts() {
     discovered_contracts=()
+    # Byte order, exactly as the runner discovers them. A UTF-8 collation folds
+    # the punctuation away and reorders the pairs that differ only by `-` and
+    # `_`, so a manifest correct here would be wrong on a machine with a
+    # different LANG.
     while IFS= read -r path; do
         [[ -x "$path" || "$path" == *_test.py ]] || continue
         discovered_contracts+=("tests/${path#"$repo_dir/tests/"}")
     done < <(find "$repo_dir/tests" -type f \
-        -not -path '*/fixtures/*' -not -path '*__pycache__*' | sort)
+        -not -path '*/fixtures/*' -not -path '*__pycache__*' | LC_ALL=C sort)
 }
 
 validate_manifest() {
     local candidate="$1"
     local -n expected_contracts="$2"
+    # Byte order, for the same reason discover_contracts sorts in it.
+    local LC_ALL=C
     local line capabilities path extra previous_comment="" previous_was_comment=0
     local -a capability_list=()
     local -A manifest_paths=() capability_counts=()