diff --git a/elasticapm/conf/__init__.py b/elasticapm/conf/__init__.py
index 5318d64b5..5b851c9a5 100644
--- a/elasticapm/conf/__init__.py
+++ b/elasticapm/conf/__init__.py
@@ -275,7 +275,14 @@ def __call__(self, value, field_name):
         match = re.match(self.regex, value)
         if match:
             return value
-        raise ConfigurationError("{} does not match pattern {}".format(value, self.verbose_pattern), field_name)
+        raise ConfigurationError(
+            "{}={} does not match pattern {}".format(
+                field_name,
+                value,
+                self.verbose_pattern,
+            ),
+            field_name,
+        )
 
 
 class UnitValidator(object):
@@ -288,12 +295,19 @@ def __call__(self, value, field_name):
         value = str(value)
         match = re.match(self.regex, value, re.IGNORECASE)
         if not match:
-            raise ConfigurationError("{} does not match pattern {}".format(value, self.verbose_pattern), field_name)
+            raise ConfigurationError(
+                "{}={} does not match pattern {}".format(
+                    field_name,
+                    value,
+                    self.verbose_pattern,
+                ),
+                field_name,
+            )
         val, unit = match.groups()
         try:
             val = int(val) * self.unit_multipliers[unit]
         except KeyError:
-            raise ConfigurationError("{} is not a supported unit".format(unit), field_name)
+            raise ConfigurationError("{}={} is not a supported unit".format(field_name, unit), field_name)
         return val
 
 
@@ -315,7 +329,7 @@ def __call__(self, value, field_name):
         try:
             value = float(value)
         except ValueError:
-            raise ConfigurationError("{} is not a float".format(value), field_name)
+            raise ConfigurationError("{}={} is not a float".format(field_name, value), field_name)
         multiplier = 10**self.precision
         rounded = math.floor(value * multiplier + 0.5) / multiplier
         if rounded == 0 and self.minimum and value != 0:
@@ -337,8 +351,10 @@ def __init__(self, range_start, range_end, range_desc) -> None:
     def __call__(self, value, field_name):
         if self.range_start <= value <= self.range_end:
             raise ConfigurationError(
-                "{} cannot be in range: {}".format(
-                    value, self.range_desc.format(**{"range_start": self.range_start, "range_end": self.range_end})
+                "{}={} cannot be in range: {}".format(
+                    field_name,
+                    value,
+                    self.range_desc.format(**{"range_start": self.range_start, "range_end": self.range_end}),
                 ),
                 field_name,
             )
@@ -349,11 +365,11 @@ class FileIsReadableValidator(object):
     def __call__(self, value, field_name):
         value = os.path.normpath(value)
         if not os.path.exists(value):
-            raise ConfigurationError("{} does not exist".format(value), field_name)
+            raise ConfigurationError("{}={} does not exist".format(field_name, value), field_name)
         elif not os.path.isfile(value):
-            raise ConfigurationError("{} is not a file".format(value), field_name)
+            raise ConfigurationError("{}={} is not a file".format(field_name, value), field_name)
         elif not os.access(value, os.R_OK):
-            raise ConfigurationError("{} is not readable".format(value), field_name)
+            raise ConfigurationError("{}={} is not readable".format(field_name, value), field_name)
         return value
 
 
@@ -384,7 +400,12 @@ def __call__(self, value, field_name):
             ret = self.valid_values.get(value.lower())
         if ret is None:
             raise ConfigurationError(
-                "{} is not in the list of valid values: {}".format(value, list(self.valid_values.values())), field_name
+                "{}={} is not in the list of valid values: {}".format(
+                    field_name,
+                    value,
+                    list(self.valid_values.values()),
+                ),
+                field_name,
             )
         return ret