diff --git a/ruby/ql/lib/codeql/ruby/frameworks/core/Kernel.qll b/ruby/ql/lib/codeql/ruby/frameworks/core/Kernel.qll
index cc3ce9feb97..96568e74902 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/core/Kernel.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/core/Kernel.qll
@@ -135,11 +135,8 @@ module Kernel {
    * spawn([env,] command... [,options]) -> pid
    * ```
    */
-  class KernelSpawnCall extends SystemCommandExecution::Range instanceof DataFlow::CallNode {
-    KernelSpawnCall() {
-      this.getMethodName() = "spawn" and
-      this instanceof KernelMethodCall
-    }
+  class KernelSpawnCall extends SystemCommandExecution::Range instanceof KernelMethodCall {
+    KernelSpawnCall() { this.getMethodName() = "spawn" }
 
     override DataFlow::Node getAnArgument() { result = super.getArgument(_) }
 
diff --git a/ruby/ql/lib/codeql/ruby/frameworks/stdlib/Open3.qll b/ruby/ql/lib/codeql/ruby/frameworks/stdlib/Open3.qll
index f2eb16d2aa8..16b9ecc3797 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/stdlib/Open3.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/stdlib/Open3.qll
@@ -31,6 +31,11 @@ module Open3 {
     }
   }
 
+  /**
+   * A system command executed via one of the `Open4` methods.
+   * These methods take the same argument forms as `Kernel.system`.
+   * See `KernelSystemCall` for details.
+   */
   class Open4Call extends SystemCommandExecution::Range instanceof DataFlow::CallNode {
     Open4Call() {
       this = API::getTopLevelMember("Open4").getAMethodCall(["open4", "popen4", "spawn"])