diff --git a/src/ert/resources/forward-models/res/script/ecl_run.py b/src/ert/resources/forward-models/res/script/ecl_run.py
index 93dec112d2b..6975da5d632 100644
--- a/src/ert/resources/forward-models/res/script/ecl_run.py
+++ b/src/ert/resources/forward-models/res/script/ecl_run.py
@@ -280,6 +280,10 @@ def runPath(self):
     def baseName(self):
         return self.base_name
 
+    @property
+    def prt_path(self):
+        return Path(self.run_path) / (self.baseName() + ".PRT")
+
     def numCpu(self):
         return self.num_cpu
 
@@ -489,6 +493,7 @@ def summary_block(self):
         return ecl_sum
 
     def assertECLEND(self):
+        tail_length = 5000
         result = self.readECLEND()
         if result.errors > 0:
             error_list = self.parseErrors()
@@ -502,7 +507,9 @@ def assertECLEND(self):
                 extra_message = (
                     f"\n\nWarning, mismatch between stated Error count ({result.errors}) "
                     f"and number of ERROR messages found in PRT ({len(error_messages)})."
-                )
+                    f"\n\nTail ({tail_length} bytes) of PRT-file {self.prt_path}:\n\n"
+                ) + tail_textfile(self.prt_path, 5000)
+
             raise EclError(
                 "Eclipse simulation failed with:"
                 f"{result.errors:d} errors:\n\n{error_and_slave_msg}{extra_message}"
@@ -517,7 +524,7 @@ def readECLEND(self):
 
         report_file = os.path.join(self.run_path, f"{self.base_name}.ECLEND")
         if not os.path.isfile(report_file):
-            report_file = os.path.join(self.run_path, f"{self.base_name}.PRT")
+            report_file = self.prt_path
 
         errors = None
         bugs = None
@@ -539,12 +546,11 @@ def readECLEND(self):
 
     def parseErrors(self) -> List[str]:
         """Extract multiline ERROR messages from the PRT file"""
-        prt_file = os.path.join(self.runPath(), f"{self.baseName()}.PRT")
         error_list = []
         error_e100_regexp = re.compile(error_pattern_e100, re.MULTILINE)
         error_e300_regexp = re.compile(error_pattern_e300, re.MULTILINE)
         slave_started_regexp = re.compile(slave_started_pattern, re.MULTILINE)
-        with open(prt_file, "r", encoding="utf-8") as filehandle:
+        with open(self.prt_path, "r", encoding="utf-8") as filehandle:
             content = filehandle.read()
 
         for regexp in [error_e100_regexp, error_e300_regexp, slave_started_regexp]:
@@ -604,3 +610,14 @@ def run(config: EclConfig, argv):
     except EclError as msg:
         print(msg, file=sys.stderr)
         sys.exit(-1)
+
+
+def tail_textfile(file_path: Path, num_chars: int) -> str:
+    if not file_path.exists():
+        return f"No output file {file_path}"
+    with open(file_path, encoding="utf-8") as file:
+        file.seek(0, 2)
+        file_end_position = file.tell()
+        seek_position = max(0, file_end_position - num_chars)
+        file.seek(seek_position)
+        return file.read()[-num_chars:]
diff --git a/tests/unit_tests/resources/test_ecl_run_new_config.py b/tests/unit_tests/resources/test_ecl_run_new_config.py
index b1e4222a676..59ff4ccaa51 100644
--- a/tests/unit_tests/resources/test_ecl_run_new_config.py
+++ b/tests/unit_tests/resources/test_ecl_run_new_config.py
@@ -525,6 +525,37 @@ def test_too_few_parsed_error_messages_gives_warning():
     assert "Warning, mismatch between stated Error count" in str(exception_info.value)
 
 
+@pytest.mark.usefixtures("use_tmpdir")
+def test_tail_of_prt_file_is_included_when_error_count_inconsistency():
+    prt_error = (
+        "this_should_not_be_included "
+        + "\n" * 10000
+        + """
+  this_should_be_included
+
+ @--MESSAGE  AT TIME        0.0   DAYS    ( 1-JAN-2000):
+ @           THIS IS JUST A MESSAGE, NOTHING ELSE"""
+    )
+    eclend = """
+ Error summary
+ Comments               0
+ Warnings               0
+ Problems               0
+ Errors                 1
+ Bugs                   0"""
+
+    Path("ECLCASE.PRT").write_text(prt_error + "\n" + eclend, encoding="utf-8")
+    Path("ECLCASE.ECLEND").write_text(eclend, encoding="utf-8")
+
+    Path("ECLCASE.DATA").write_text("", encoding="utf-8")
+
+    run = ecl_run.EclRun("ECLCASE.DATA", "dummysimulatorobject")
+    with pytest.raises(ecl_run.EclError) as exception_info:
+        run.assertECLEND()
+    assert "this_should_be_included" in str(exception_info.value)
+    assert "this_should_not_be_included" not in str(exception_info.value)
+
+
 @pytest.mark.usefixtures("use_tmpdir")
 def test_correct_number_of_parsed_error_messages_gives_no_warning():
     prt_error = """\