diff --git a/README.md b/README.md
index cbd141a..40701c3 100644
--- a/README.md
+++ b/README.md
@@ -76,7 +76,7 @@ Optional:
 3. Remove duplicates by applying an undo/redo JSON file
 
   ```sh
-  orcli transform "duplicates" "https://git.io/fj5hF"
+  orcli transform "duplicates" "https://git.io/fj5ju"
   ```
 
 4. Export data from OpenRefine project to tab-separated-values (TSV) file `duplicates.tsv`
diff --git a/orcli b/orcli
index 8287b81..6495723 100755
--- a/orcli
+++ b/orcli
@@ -887,10 +887,17 @@ orcli_transform_command() {
   # support multiple files
   for i in "${!files[@]}"; do
       # read each operation into one line
-      mapfile -t jsonlines < <(jq -c '.[]' "${files[$i]}")
+      if json="$(jq -c '.[]' "${files[$i]}")"; then
+          mapfile -t jsonlines <<<"$json"
+      else
+          error "parsing ${files[$i]} failed!"
+      fi
       for line in "${jsonlines[@]}"; do
           # parse one line/operation into array
           declare -A data="($(echo "$line" | jq -r 'to_entries | map("[\(.key)]=" + @sh "\(.value|tostring)") | .[]'))"
+          if [[ ! ${data[op]} ]]; then
+              error "parsing ${files[$i]} failed!"
+          fi
           # map operation names to command endpoints
           # https://github.com/OpenRefine/OpenRefine/blob/master/main/webapp/modules/core/MOD-INF/controller.js
           com="${data[op]#core/}"
diff --git a/src/transform_command.sh b/src/transform_command.sh
index fde2047..8da451a 100644
--- a/src/transform_command.sh
+++ b/src/transform_command.sh
@@ -29,10 +29,17 @@ done
 # support multiple files
 for i in "${!files[@]}"; do
     # read each operation into one line
-    mapfile -t jsonlines < <(jq -c '.[]' "${files[$i]}")
+    if json="$(jq -c '.[]' "${files[$i]}")"; then
+        mapfile -t jsonlines <<<"$json"
+    else
+        error "parsing ${files[$i]} failed!"
+    fi
     for line in "${jsonlines[@]}"; do
         # parse one line/operation into array
         declare -A data="($(echo "$line" | jq -r 'to_entries | map("[\(.key)]=" + @sh "\(.value|tostring)") | .[]'))"
+        if [[ ! ${data[op]} ]]; then
+            error "parsing ${files[$i]} failed!"
+        fi
         # map operation names to command endpoints
         # https://github.com/OpenRefine/OpenRefine/blob/master/main/webapp/modules/core/MOD-INF/controller.js
         com="${data[op]#core/}"