diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -200,8 +200,8 @@
     set(FLANG_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
   endif()
 
-  set(MLIR_MAIN_SRC_DIR ${LLVM_MAIN_SRC_DIR}/../mlir/include ) # --src-root
-  set(MLIR_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../mlir/include ) # --includedir
+  set(MLIR_MAIN_SRC_DIR ${LLVM_MAIN_SRC_DIR}/../mlir ) # --src-root
+  set(MLIR_INCLUDE_DIR ${MLIR_MAIN_SRC_DIR}/include ) # --includedir
   set(MLIR_TABLEGEN_OUTPUT_DIR ${CMAKE_BINARY_DIR}/tools/mlir/include)
   include_directories(SYSTEM ${MLIR_INCLUDE_DIR})
   include_directories(SYSTEM ${MLIR_TABLEGEN_OUTPUT_DIR})
diff --git a/flang/include/flang/Optimizer/Dialect/CMakeLists.txt b/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
--- a/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
+++ b/flang/include/flang/Optimizer/Dialect/CMakeLists.txt
@@ -26,7 +26,7 @@
 set(dialect_doc_filename "FIRLangRef")
 
 set(LLVM_TARGET_DEFINITIONS FIROps.td)
-tablegen(MLIR ${dialect_doc_filename}.md -gen-op-doc "-I${MLIR_MAIN_SRC_DIR}" "-I${MLIR_INCLUDE_DIR}")
+tablegen(MLIR ${dialect_doc_filename}.md -gen-op-doc "-I${MLIR_INCLUDE_DIR}")
 set(GEN_DOC_FILE ${FLANG_BINARY_DIR}/docs/Dialect/${dialect_doc_filename}.md)
 add_custom_command(
         OUTPUT ${GEN_DOC_FILE}