diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9b3f2d72..de8084a96 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 BUG FIXES:
 * Fixed default provider organization usage for `r/tfe_admin_organization_settings`, by @brandonc [1183](https://github.com/hashicorp/terraform-provider-tfe/pull/1183)
+* `/r/tfe_workspace_settings`: Fix compatibility with older versions of Terraform Enterprise when using agent execution by @brandonc [1193](https://github.com/hashicorp/terraform-provider-tfe/pull/1193)
 
 # v0.51.0
 
diff --git a/internal/provider/resource_tfe_workspace_settings.go b/internal/provider/resource_tfe_workspace_settings.go
index f8ab6653b..f6fabaff6 100644
--- a/internal/provider/resource_tfe_workspace_settings.go
+++ b/internal/provider/resource_tfe_workspace_settings.go
@@ -166,9 +166,11 @@ func (m unknownIfExecutionModeUnset) PlanModifyString(ctx context.Context, req p
 		if configured.ExecutionMode.IsNull() && overwritesState[0].ExecutionMode.ValueBool() {
 			resp.PlanValue = types.StringUnknown()
 		}
-	} else if req.Path.Equal(path.Root("execution_mode")) {
+	} else if configured.ExecutionMode.IsNull() && req.Path.Equal(path.Root("execution_mode")) {
 		// TFE does not support overwrites so default the execution mode to "remote"
 		resp.PlanValue = types.StringValue("remote")
+	} else if configured.AgentPoolID.IsNull() && req.Path.Equal(path.Root("agent_pool_id")) {
+		resp.PlanValue = types.StringNull()
 	}
 }