Index: flang/tools/f18/flang
===================================================================
--- flang/tools/f18/flang
+++ flang/tools/f18/flang
@@ -284,17 +284,15 @@
   local -n opts=$3
 
   local ext_fc=""
-  if [[ -v $FLANG_FC ]]; then
+  if [[ -v FLANG_FC ]]; then
     ext_fc="${FLANG_FC}"
-  elif [[ -v $F18_FC ]]; then
+  elif [[ -v F18_FC ]]; then
     # We support F18_FC for backwards compatibility.
     ext_fc="${F18_FC}"
   else
     ext_fc=gfortran
   fi
 
-
-  local ext_fc="${FLANG_FC:-gfortran}"
   local -r wd=$(cd "$(dirname "$0")/.." && pwd)
 
   # Use the provided output file name.
@@ -417,7 +415,15 @@
   done
 
   # STEP 2: Compile Fortran Source Files
-  readonly ext_fc="${F18_FC:-gfortran}"
+  local ext_fc=""
+  if [[ -v FLANG_FC ]]; then
+    ext_fc="${FLANG_FC}"
+  elif [[ -v F18_FC ]]; then
+    # We support F18_FC for backwards compatibility.
+    ext_fc="${F18_FC}"
+  else
+    ext_fc=gfortran
+  fi
   # Temporary object files generated by this script. To be deleted at the end.
   local temp_object_files=()
   for idx in "${!fortran_source_files[@]}"; do