diff --git a/spacy/errors.py b/spacy/errors.py
index 9a8cf63c9..96e84ef8d 100644
--- a/spacy/errors.py
+++ b/spacy/errors.py
@@ -972,6 +972,8 @@ class Errors(metaclass=ErrorsWithCodes):
     E1051 = ("'allow_overlap' can only be False when max_positive is 1, but found 'max_positive': {max_positive}.")
     E1052 = ("Both 'min_length' and 'max_length' should be larger than 1, but found"
              " 'min_length': {min_length}, 'max_length': {max_length}")
+    E1053 = ("Text, including whitespace, must match between reference and "
+             "predicted docs when training {component}.")
 
 
 # Deprecated model shortcuts, only used in errors and warnings
diff --git a/spacy/pipeline/span_finder.py b/spacy/pipeline/span_finder.py
index 4aa526c5a..258781be0 100644
--- a/spacy/pipeline/span_finder.py
+++ b/spacy/pipeline/span_finder.py
@@ -294,6 +294,8 @@ class SpanFinder(TrainablePipe):
         reference_truths = []
 
         for eg in examples:
+            if eg.x.text != eg.y.text:
+                raise ValueError(Errors.E1053.format(component="span_finder"))
             start_indices = set()
             end_indices = set()