diff --git a/madoop/mapreduce.py b/madoop/mapreduce.py
index bac9193..4e4ec1f 100644
--- a/madoop/mapreduce.py
+++ b/madoop/mapreduce.py
@@ -213,7 +213,6 @@ def map_single_chunk(exe, input_path, output_path, chunk):
                 f"Command returned non-zero: "
                 f"{exe} < {input_path} > {output_path}\n"
                 f"{err}\n"
-                f"{err.stdout.decode()}" if err.stdout else ""
                 f"{err.stderr.decode()}" if err.stderr else ""
             ) from err
         except OSError as err:
@@ -342,10 +341,8 @@ def partition_keys_custom(
         return_code = process.wait()
         if return_code:
             stderr_output = process.stderr.read()
-            if len(stderr_output) != 0:
-                stderr_output = '\n' + stderr_output
             raise MadoopError(
-                f"Partition executable returned non-zero: {str(partitioner)}"
+                f"Partition executable returned non-zero: {str(partitioner)}\n"
                 f"{stderr_output}"
             )
 
@@ -445,7 +442,6 @@ def reduce_single_file(exe, input_path, output_path):
                 f"Command returned non-zero: "
                 f"{exe} < {input_path} > {output_path}\n"
                 f"{err}\n"
-                f"{err.stdout.decode()}" if err.stdout else ""
                 f"{err.stderr.decode()}" if err.stderr else ""
             ) from err
         except OSError as err:
diff --git a/tests/testdata/word_count/map_error_msg.py b/tests/testdata/word_count/map_error_msg.py
index 722cf8a..8d584d9 100755
--- a/tests/testdata/word_count/map_error_msg.py
+++ b/tests/testdata/word_count/map_error_msg.py
@@ -7,6 +7,5 @@
 # Avoid error on executable check which has an empty string input
 input_lines_n = sum(1 for _ in sys.stdin)
 if input_lines_n > 1:
-    sys.stdout.write("Map error message to stdout\n")
     sys.stderr.write("Map error message to stderr\n")
     sys.exit(1)
diff --git a/tests/testdata/word_count/reduce_error_msg.py b/tests/testdata/word_count/reduce_error_msg.py
index d7bdd31..6d92b0c 100755
--- a/tests/testdata/word_count/reduce_error_msg.py
+++ b/tests/testdata/word_count/reduce_error_msg.py
@@ -7,6 +7,5 @@
 # Avoid error on executable check which has an empty string input
 input_lines_n = sum(1 for _ in sys.stdin)
 if input_lines_n > 1:
-    sys.stdout.write("Reduce error message to stdout\n")
     sys.stderr.write("Reduce error message to stderr\n")
     sys.exit(1)