diff --git a/packages/dd-trace/src/profiling/config.js b/packages/dd-trace/src/profiling/config.js
index 8d399c68bf5..538400aaa7a 100644
--- a/packages/dd-trace/src/profiling/config.js
+++ b/packages/dd-trace/src/profiling/config.js
@@ -97,6 +97,11 @@ class Config {
     const samplingContextsAvailable = process.platform !== 'win32'
     function checkOptionAllowed (option, description, condition) {
       if (option && !condition) {
+        // injection hardening: all of these can only happen if user explicitly
+        // sets an environment variable to its non-default value on the platform.
+        // In practical terms, it'd require someone explicitly turning on OOM
+        // monitoring, code hotspots, endpoint profiling, or CPU profiling on
+        // Windows, where it is not supported.
         throw new Error(`${description} not supported on ${process.platform}.`)
       }
     }
diff --git a/packages/dd-trace/src/profiling/ssi-heuristics.js b/packages/dd-trace/src/profiling/ssi-heuristics.js
index 9910b9273bc..4790ae2b9b5 100644
--- a/packages/dd-trace/src/profiling/ssi-heuristics.js
+++ b/packages/dd-trace/src/profiling/ssi-heuristics.js
@@ -3,6 +3,7 @@
 const telemetryMetrics = require('../telemetry/metrics')
 const profilersNamespace = telemetryMetrics.manager.namespace('profilers')
 const dc = require('dc-polyfill')
+const log = require('../log')
 
 // If the process lives for at least 30 seconds, it's considered long-lived
 const DEFAULT_LONG_LIVED_THRESHOLD = 30000
@@ -40,9 +41,14 @@ class SSIHeuristics {
 
     const longLivedThreshold = config.profiling.longLivedThreshold || DEFAULT_LONG_LIVED_THRESHOLD
     if (typeof longLivedThreshold !== 'number' || longLivedThreshold <= 0) {
-      throw new Error('Long-lived threshold must be a positive number')
+      this.longLivedThreshold = DEFAULT_LONG_LIVED_THRESHOLD
+      log.warn(
+        `Invalid SSIHeuristics.longLivedThreshold value: ${config.profiling.longLivedThreshold}. ` +
+        `Using default value: ${DEFAULT_LONG_LIVED_THRESHOLD}`
+      )
+    } else {
+      this.longLivedThreshold = longLivedThreshold
     }
-    this.longLivedThreshold = longLivedThreshold
 
     this.hasSentProfiles = false
     this.noSpan = true
@@ -94,6 +100,8 @@ class SSIHeuristics {
         })
         break
       default:
+        // injection hardening: only usage is internal, one call site with
+        // a function and another with undefined, so we can throw here.
         throw new TypeError('callback must be a function or undefined')
     }
   }
diff --git a/packages/dd-trace/src/proxy.js b/packages/dd-trace/src/proxy.js
index c3b865226ed..dd30fa89c88 100644
--- a/packages/dd-trace/src/proxy.js
+++ b/packages/dd-trace/src/proxy.js
@@ -202,6 +202,7 @@ class Tracer extends NoopProxy {
 
   profilerStarted () {
     if (!this._profilerStarted) {
+      // injection hardening: this is only ever invoked from tests.
       throw new Error('profilerStarted() must be called after init()')
     }
     return this._profilerStarted