diff --git a/cpp/src/arrow/CMakeLists.txt b/cpp/src/arrow/CMakeLists.txt
index 1234567..abcdefg 100644
--- a/cpp/src/arrow/CMakeLists.txt
+++ b/cpp/src/arrow/CMakeLists.txt
@@ -173,7 +173,7 @@ list(APPEND ARROW_STATIC_INSTALL_INTERFACE_LIBS ${ARROW_SYSTEM_LINK_LIBS})
 
 # Need -latomic on Raspbian.
 # See also: https://issues.apache.org/jira/browse/ARROW-12860
-if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux" AND ${CMAKE_SYSTEM_PROCESSOR} MATCHES "armv7")
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" AND "${CMAKE_SYSTEM_PROCESSOR}" MATCHES "armv7")
   string(APPEND ARROW_PC_LIBS_PRIVATE " -latomic")
   list(APPEND ARROW_SHARED_INSTALL_INTERFACE_LIBS "atomic")
   list(APPEND ARROW_STATIC_INSTALL_INTERFACE_LIBS "atomic")
diff --git a/cpp/src/arrow/acero/source_node.cc b/cpp/src/arrow/acero/source_node.cc
index 0f5840676..cf68bfdcb 100644
--- a/cpp/src/arrow/acero/source_node.cc
+++ b/cpp/src/arrow/acero/source_node.cc
@@ -407,7 +407,7 @@ struct SchemaSourceNode : public SourceNode {
 struct RecordBatchReaderSourceNode : public SourceNode {
   RecordBatchReaderSourceNode(ExecPlan* plan, std::shared_ptr<Schema> schema,
                               arrow::AsyncGenerator<std::optional<ExecBatch>> generator)
-      : SourceNode(plan, schema, generator) {}
+      : SourceNode(plan, schema, generator, Ordering::Implicit()) {}
 
   static Result<ExecNode*> Make(ExecPlan* plan, std::vector<ExecNode*> inputs,
                                 const ExecNodeOptions& options) {