diff --git a/Fortran/UnitTests/fcvs21_f95/CMakeLists.txt b/Fortran/UnitTests/fcvs21_f95/CMakeLists.txt
--- a/Fortran/UnitTests/fcvs21_f95/CMakeLists.txt
+++ b/Fortran/UnitTests/fcvs21_f95/CMakeLists.txt
@@ -12,6 +12,9 @@
 # Thread model: posix
 # gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
 #
+# Reference results for tests 905 and 907 generated with flang ~15.0.0 on
+# Ubuntu 20.04 (aarch64-unknown-linux-gnu).
+#
 # See additional comments in `driver_run` script should reference
 # results ever need to be updated.
 #
@@ -33,19 +36,23 @@
 # clean-up fort.* files otherwise one of the tests will fail
 llvm_test_prepare(rm -f %S/fort.*)
 
+# Different compilers or different compiler options may produce slightly
+# different but still valid outputs for some of these tests. By default, we will
+# check that the outputs match the reference outputs exactly. However, when this
+# option is set, we will check less strictly.
+option(FCVS_ALLOW_FLEXIBLE_OUTPUT "Don't match the output of FCVS tests exactly")
+
 # Group 1:
 # Tests 905 and 907 use list-directed output, for which the standard allows some
 # flexibility, e.g., with regards to how many white space characters or
 # floating point decimals to print. Treat them separately.
-# FIXME: Reenable these tests after moving the buildbots from using
-# flang-to-external-fc to using flang-new.
 set(SPECIAL_CASES "FM905.f" "FM907.f")
-if (NOT CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
-  set(Source ${SPECIAL_CASES})
+set(Source ${SPECIAL_CASES})
+if (FCVS_ALLOW_FLEXIBLE_OUTPUT)
   set(FP_IGNOREWHITESPACE ON)
-  llvm_singlesource()
-  set(Source)
 endif()
+llvm_singlesource()
+set(Source)
 
 # Group 2:
 # Generic case. Make sure to exclude the special cases which have already been
diff --git a/Fortran/UnitTests/fcvs21_f95/FM905.reference_output b/Fortran/UnitTests/fcvs21_f95/FM905.reference_output
--- a/Fortran/UnitTests/fcvs21_f95/FM905.reference_output
+++ b/Fortran/UnitTests/fcvs21_f95/FM905.reference_output
@@ -27,22 +27,22 @@
 
      1    INSPECT
                  COMPUTED= 
-           2
+ 2
                  CORRECT=  
        2
      2    INSPECT
                  COMPUTED= 
-           1           3           5           7           9
+ 1 3 5 7 9
                  CORRECT=  
        1  3  5  7  9
      3    INSPECT
                  COMPUTED= 
-   2.50000000    
+ 2.5
                  CORRECT=  
        2.5
      4    INSPECT
                  COMPUTED= 
-   2.50000003E-11  0.250000000       250.000000       2.50000000E+09
+ 2.5E-11 .25 250. 2.5E+09
                  CORRECT=  
         2.5E-11  0.25  250.0   2.5E+09
      5    INSPECT
@@ -57,7 +57,7 @@
        ONE  TWO  THREEFOUR 
      7    INSPECT
                  COMPUTED= 
-          -3   15.2500000     HELLO T
+ -3 15.25 HELLO T
                  CORRECT=  
        -3  15.25  HELLO  T
      8    INSPECT
@@ -67,13 +67,14 @@
        5 O'CLOCK
      9    INSPECT
                  COMPUTED= 
- SHORTTHIS IS A LONGER CHARACTER STRING123456789012345678901234567890123456789012345678901234567890123456789012          
+ SHORTTHIS IS A LONGER CHARACTER STRING1234567890123456789012345678901234567890
+ 12345678901234567890123456789012          
                  CORRECT=  
  SHORT  THIS IS A LONGER CHARACTER STRING 123456789012345678901234567890123456789
  012345678901234567890123456789012
     10    INSPECT
                  COMPUTED= 
-           5           5           5           5           5
+ 5 5 5 5 5
                  CORRECT=  
        5  5  5  5  5  OR  5*5
  
diff --git a/Fortran/UnitTests/fcvs21_f95/FM907.reference_output b/Fortran/UnitTests/fcvs21_f95/FM907.reference_output
--- a/Fortran/UnitTests/fcvs21_f95/FM907.reference_output
+++ b/Fortran/UnitTests/fcvs21_f95/FM907.reference_output
@@ -29,42 +29,42 @@
 
      1    INSPECT
                  COMPUTED= 
-   2.5000000000000000     
+ 2.5
                  CORRECT=  
        2.5
      2    INSPECT
                  COMPUTED= 
-             (3.00000000,4.00000000)
+ (3.,4.)
                  CORRECT=  
         (3.0,4.0)
      3    INSPECT
                  COMPUTED= 
-   2.5000000000000000        2.5000000000000002E-010   25000000000.000000     
+ 2.5 2.5E-10 25000000000.
                  CORRECT=  
        2.5  2.5D-10  2.5D+10
      4    INSPECT
                  COMPUTED= 
-             (0.00000000,1.00000000)             (8.00000000,10.0000000)            (-5.00000000,0.00000000)             (0.00000000,0.00000000)
+ (0.,1.) (8.,10.) (-5.,0.) (0.,0.)
                  CORRECT=  
         (0.0,1.0)   (8.0,10.0)   (-5.0,0.0)   (0.0,0.0)
      5    INSPECT
                  COMPUTED= 
-             (3.00000000,4.00000000)   5.0000000000000000       -5.0000000000000000                (-3.00000000,-4.00000000)
+ (3.,4.) 5. -5. (-3.,-4.)
                  CORRECT=  
         (3.0,4.0)  5.0  -5.0   (-3.0,-4.0)
      6    INSPECT
                  COMPUTED= 
-             (6.00000000,9.00000000)
+ (6.,9.)
                  CORRECT=  
         (6.0,9.0)
      7    INSPECT
                  COMPUTED= 
-   3.25000000    
+ 3.25
                  CORRECT=  
        3.25
      8    INSPECT
                  COMPUTED= 
-            (2.00000000,-3.00000000) T   15.6250000     GOODBYE FOR NOW
+ (2.,-3.) T 15.625 GOODBYE FOR NOW
                  CORRECT=  
         (2.0,-3.0)  T  15.625  GOODBYE  FOR NOW