diff --git a/api/jsep.cc b/api/jsep.cc
index ddb39b6181..5fdc8905c7 100644
--- a/api/jsep.cc
+++ b/api/jsep.cc
@@ -21,23 +21,6 @@ size_t SessionDescriptionInterface::RemoveCandidates(
   return 0;
 }
 
-void CreateSessionDescriptionObserver::OnFailure(RTCError error) {
-  OnFailure(error.message());
-}
-
-void CreateSessionDescriptionObserver::OnFailure(const std::string& error) {
-  OnFailure(RTCError(RTCErrorType::INTERNAL_ERROR, std::string(error)));
-}
-
-void SetSessionDescriptionObserver::OnFailure(RTCError error) {
-  std::string message(error.message());
-  OnFailure(message);
-}
-
-void SetSessionDescriptionObserver::OnFailure(const std::string& error) {
-  OnFailure(RTCError(RTCErrorType::INTERNAL_ERROR, std::string(error)));
-}
-
 const char SessionDescriptionInterface::kOffer[] = "offer";
 const char SessionDescriptionInterface::kPrAnswer[] = "pranswer";
 const char SessionDescriptionInterface::kAnswer[] = "answer";
diff --git a/api/jsep.h b/api/jsep.h
index 86f4162f84..cf8aeb0cb4 100644
--- a/api/jsep.h
+++ b/api/jsep.h
@@ -28,6 +28,7 @@
 
 #include "absl/types/optional.h"
 #include "api/rtc_error.h"
+#include "rtc_base/deprecation.h"
 #include "rtc_base/ref_count.h"
 #include "rtc_base/system/rtc_export.h"
 
@@ -222,11 +223,9 @@ class RTC_EXPORT CreateSessionDescriptionObserver
   // error code and a string.
   // RTCError is non-copyable, so it must be passed using std::move.
   // Earlier versions of the API used a string argument. This version
-  // is deprecated; in order to let clients remove the old version, it has a
-  // default implementation. If both versions are unimplemented, the
-  // result will be a runtime error (stack overflow). This is intentional.
-  virtual void OnFailure(RTCError error);
-  virtual void OnFailure(const std::string& error);
+  // is removed; its functionality was the same as passing
+  // error.message.
+  virtual void OnFailure(RTCError error) = 0;
 
  protected:
   ~CreateSessionDescriptionObserver() override = default;
@@ -237,9 +236,7 @@ class RTC_EXPORT SetSessionDescriptionObserver : public rtc::RefCountInterface {
  public:
   virtual void OnSuccess() = 0;
   // See description in CreateSessionDescriptionObserver for OnFailure.
-  virtual void OnFailure(RTCError error);
-
-  virtual void OnFailure(const std::string& error);
+  virtual void OnFailure(RTCError error) = 0;
 
  protected:
   ~SetSessionDescriptionObserver() override = default;