diff --git a/bilby/core/prior.py b/bilby/core/prior.py
index 5e6894e740a2c272a7dac7d8c8eac7e1ee1cbaae..aca8e710e1f0fb741ff281e1053a00b2c24253d8 100644
--- a/bilby/core/prior.py
+++ b/bilby/core/prior.py
@@ -115,7 +115,12 @@ class PriorDict(OrderedDict):
                 elements = line.split('=')
                 key = elements[0].replace(' ', '')
                 val = '='.join(elements[1:])
-                prior[key] = eval(val)
+                try:
+                    prior[key] = eval(val)
+                except TypeError as e:
+                    raise TypeError(
+                        "Unable to parse dictionary file {}, bad line: {} = {}. Error message {}"
+                        .format(filename, key, val, e))
         self.update(prior)
 
     def from_dictionary(self, dictionary):