diff --git a/g3doc/user_guide/gpu.md b/g3doc/user_guide/gpu.md
index 584a4a3a0..b0e3a5bfa 100644
--- a/g3doc/user_guide/gpu.md
+++ b/g3doc/user_guide/gpu.md
@@ -207,8 +207,8 @@ Please
 [open a GitHub issue](https://github.com/google/gvisor/issues/new?labels=type%3A+bug,area%3A+gpu&template=bug_report.yml)
 to describe about your use case. If a missing `ioctl` implementation is the
 problem, then the [debug logs](/docs/user_guide/debugging/) will contain
-warnings with prefix `nvproxy: unknown *`. See below on how to run the
-`ioctl_sniffer` tool.
+warnings with prefix `nvproxy: handler is undefined *`. See below on how to run
+the `ioctl_sniffer` tool.
 
 ### Debugging
 
diff --git a/pkg/sentry/devices/nvproxy/frontend.go b/pkg/sentry/devices/nvproxy/frontend.go
index 9e6a2d180..d1eb081b8 100644
--- a/pkg/sentry/devices/nvproxy/frontend.go
+++ b/pkg/sentry/devices/nvproxy/frontend.go
@@ -450,7 +450,7 @@ func rmAllocMemory(fi *frontendIoctlState) (uintptr, error) {
 	case nvgpu.NV01_MEMORY_SYSTEM_OS_DESCRIPTOR:
 		return rmAllocOSDescriptor(fi, &ioctlParams)
 	default:
-		fi.ctx.Warningf("nvproxy: unknown NV_ESC_RM_ALLOC_MEMORY class %v", ioctlParams.Params.HClass)
+		fi.ctx.Warningf("nvproxy: %s for NV_ESC_RM_ALLOC_MEMORY class %v", errUndefinedHandler.Error(), ioctlParams.Params.HClass)
 		return 0, linuxerr.EINVAL
 	}
 }
@@ -1305,7 +1305,7 @@ func rmVidHeapControl(fi *frontendIoctlState) (uintptr, error) {
 	case nvgpu.NVOS32_FUNCTION_ALLOC_SIZE:
 		return rmVidHeapControlAllocSize(fi, &ioctlParams)
 	default:
-		fi.ctx.Warningf("nvproxy: unknown VID_HEAP_CONTROL function %d", ioctlParams.Function)
+		fi.ctx.Warningf("nvproxy: %s for VID_HEAP_CONTROL function %d", errUndefinedHandler.Error(), ioctlParams.Function)
 		return 0, linuxerr.EINVAL
 	}
 }