diff --git a/src/JobShopParser/__init__.py b/src/JobShopParser/__init__.py
index b407706..9ac12e1 100644
--- a/src/JobShopParser/__init__.py
+++ b/src/JobShopParser/__init__.py
@@ -80,7 +80,7 @@ class JobShopVisitor(arpeggio.PTNodeVisitor):
         if len(job_numbers) % 2 ==1:
             raise ParseError("Odd number of numbers in job data")
         # returns list of (duration, machine) tuples
-                return list(zip(job_numbers[1::2], job_numbers[0::2])) # [::2] returns only every second element of the list
+        return list(zip(job_numbers[1::2], job_numbers[0::2])) # [::2] returns only every second element of the list
 
     def visit_problem_data(self, node: arpeggio.ParseTreeNode, children: arpeggio.SemanticActionResults) -> JobShopProblem:
         if self.debug:
diff --git a/src/JobShopParser/jobshop2_parser.py b/src/JobShopParser/jobshop2_parser.py
index 7a4c4b1..a9399e9 100644
--- a/src/JobShopParser/jobshop2_parser.py
+++ b/src/JobShopParser/jobshop2_parser.py
@@ -16,13 +16,18 @@ class JobShop2Visitor(JobShopVisitor):
 
 def parse_jobshop2_string(inputdata: str) -> JobShopProblem:
     """parse string of jobshop2-formatted data (single problem instance, no name & description)
-    and return JobShopProblem"""
-    parse_tree = parser.parse(inputdata)
+    and return JobShopProblem
+    Raises a ParseError exception on errors"""
+    try:
+        parse_tree = parser.parse(inputdata)
+    except arpeggio.NoMatch as e:
+        raise ParseError("Error while parsing problem input data at line {}, col {}:\n Rules {} did not match.".format(e.line, e.col, e.rules))
     return arpeggio.visit_parse_tree(parse_tree, JobShop2Visitor())
 
 def parse_jobshop2_file(filename: Union[str, bytes]) -> JobShopProblem:
     """Open file with jobshop2-formatted data (single problem instance, no name & description),
-    parse it and return JobShopProblem"""
+    parse it and return JobShopProblem
+    Raises a ParseError exception on errors"""
 
     with open(filename) as datafile:
         inputdata: str = datafile.read()