diff --git a/build/mach_bootstrap.py b/build/mach_bootstrap.py
index ad418a27a468..49f32d01af40 100644
--- a/build/mach_bootstrap.py
+++ b/build/mach_bootstrap.py
@@ -376,7 +376,7 @@ def bootstrap(topsrcdir, mozilla_dir=None):
                               state_dir],
                              stdout=devnull, stderr=devnull)
 
-    def populate_context(context, key=None):
+    def populate_context(key=None):
         if key is None:
             return
         if key == 'state_dir':
diff --git a/python/mach/mach/main.py b/python/mach/mach/main.py
index 69dcf85c0841..dcfd0fb0c9eb 100644
--- a/python/mach/mach/main.py
+++ b/python/mach/mach/main.py
@@ -151,7 +151,7 @@ class ContextWrapper(object):
             return getattr(object.__getattribute__(self, '_context'), key)
         except AttributeError as e:
             try:
-                ret = object.__getattribute__(self, '_handler')(self, key)
+                ret = object.__getattribute__(self, '_handler')(key)
             except (AttributeError, TypeError):
                 # TypeError is in case the handler comes from old code not
                 # taking a key argument.
@@ -320,7 +320,8 @@ To see more help for a specific command, run:
         Returns the integer exit code that should be used. 0 means success. All
         other values indicate failure.
         """
-        register_sentry()
+        topsrcdir = self.populate_context_handler('topdir')
+        register_sentry(topsrcdir)
 
         # If no encoding is defined, we default to UTF-8 because without this
         # Python 2.7 will assume the default encoding of ASCII. This will blow
@@ -401,7 +402,6 @@ To see more help for a specific command, run:
                                  commands=Registrar)
 
         if self.populate_context_handler:
-            self.populate_context_handler(context)
             context = ContextWrapper(context, self.populate_context_handler)
 
         parser = self.get_argument_parser(context)
diff --git a/python/mach/mach/sentry.py b/python/mach/mach/sentry.py
index f7a9d10b98ae..2470da08641a 100644
--- a/python/mach/mach/sentry.py
+++ b/python/mach/mach/sentry.py
@@ -6,18 +6,20 @@ from __future__ import absolute_import
 
 import os
 import re
+import sys
+from os.path import expanduser
 
+import mozpack.path as mozpath
 import sentry_sdk
-from six.moves.configparser import SafeConfigParser, NoOptionError
-
 from mozboot.util import get_state_dir
-
+from six import string_types
+from six.moves.configparser import SafeConfigParser, NoOptionError
 
 # https://sentry.prod.mozaws.net/operations/mach/
 _SENTRY_DSN = "https://8228c9aff64949c2ba4a2154dc515f55@sentry.prod.mozaws.net/525"
 
 
-def register_sentry():
+def register_sentry(topsrcdir):
     cfg_file = os.path.join(get_state_dir(), 'machrc')
     config = SafeConfigParser()
 
@@ -32,10 +34,17 @@ def register_sentry():
     if not telemetry_enabled:
         return
 
-    sentry_sdk.init(_SENTRY_DSN, before_send=_settle_mach_module_id)
+    sentry_sdk.init(_SENTRY_DSN,
+                    before_send=lambda event, _: _process_event(event, topsrcdir))
 
 
-def _settle_mach_module_id(sentry_event, exception):
+def _process_event(sentry_event, topsrcdir):
+    for map_fn in (_settle_mach_module_id, _patch_absolute_paths):
+        sentry_event = map_fn(sentry_event, topsrcdir)
+    return sentry_event
+
+
+def _settle_mach_module_id(sentry_event, _):
     # Sentry groups issues according to the stack frames and their associated
     # "module" properties. However, one of the modules is being reported
     # like "mach.commands.26a828ef5164403eaff4305ab4cb0fab" (with a generated id).
@@ -54,6 +63,50 @@ def _settle_mach_module_id(sentry_event, exception):
     return sentry_event
 
 
+def _resolve_topobjdir():
+    topobjdir = os.path.join(os.path.dirname(sys.prefix), "..")
+    return mozpath.normsep(os.path.normpath(topobjdir))
+
+
+def _patch_absolute_paths(sentry_event, topsrcdir):
+    # As discussed here (https://bugzilla.mozilla.org/show_bug.cgi?id=1636251#c28),
+    # we remove usernames from file names with a best-effort basis. The most likely
+    # place for usernames to manifest in Sentry information is within absolute paths,
+    # such as: "/home/mitch/dev/firefox/mach"
+    # We replace the state_dir, obj_dir, src_dir with "<...>" placeholders.
+    # Note that we also do a blanket find-and-replace of the user's name with "<user>",
+    # which may have ill effects if the user's name is, by happenstance, a substring
+    # of some other value within the Sentry event.
+    def recursive_patch(value, needle, replacement):
+        if isinstance(value, list):
+            return [recursive_patch(v, needle, replacement) for v in value]
+        elif isinstance(value, dict):
+            for key in list(value.keys()):
+                next_value = value.pop(key)
+                key = key.replace(needle, replacement)
+                value[key] = recursive_patch(next_value, needle, replacement)
+            return value
+        elif isinstance(value, string_types):
+            return value.replace(needle, replacement)
+        else:
+            return value
+
+    for (needle, replacement) in (
+            (get_state_dir(), "<statedir>"),
+            (_resolve_topobjdir(), "<topobjdir>"),
+            (topsrcdir, "<topsrcdir>"),
+            (expanduser("~"), "~"),
+            # Sentry converts "vars" to their "representations". When paths are in local
+            # variables on Windows, "C:\Users\MozillaUser\Desktop" becomes
+            # "'C:\\Users\\MozillaUser\\Desktop'". To still catch this case, we "repr"
+            # the home directory and scrub the beginning and end quotes, then
+            # find-and-replace on that.
+            (repr(expanduser("~"))[1:-1], "~"),
+    ):
+        sentry_event = recursive_patch(sentry_event, needle, replacement)
+    return sentry_event
+
+
 def report_exception(exception):
     # sentry_sdk won't report the exception if `sentry-sdk.init(...)` hasn't been called
     sentry_sdk.capture_exception(exception)