diff --git a/sammy/src/fin/mfin3.f90 b/sammy/src/fin/mfin3.f90
index 42cd15c645f24f0d82e79a4c523ecbb66ff73918..f9ecce0b9f4eba6ab4ef86a393b6f3be5893bff5 100644
--- a/sammy/src/fin/mfin3.f90
+++ b/sammy/src/fin/mfin3.f90
@@ -724,8 +724,15 @@ module fin3
                           Em1, Em2
          WRITE (36,10300) pair%getIa(1), pair%getIa(2), &
                           Em1, Em2
-10300    FORMAT (5X, 'Sa=', F5.1, 5X, 'Sb=', F6.1, 5x, 'Ma=', F15.8, &
-            5X, 'Mb=', F15.8)
+
+!  The precision for the printing is set high to
+!  ensure that sufficient precision for the neutron mass is
+!  available. The mass is set explictly if generating
+!  a PAR file from an ENDF file and here
+!  we need to be sure we preserve all digits available
+!  in SammyConstants
+10300    FORMAT (5X, 'Sa=', F5.1, 5X, 'Sb=', F6.1, 5x, 'Ma=', F20.15, &
+            5X, 'Mb=', F20.15)
          IF (pair%getQ().NE.Zero) THEN            
             WRITE (38,10400) pair%getQ()
             WRITE (36,10400) pair%getQ()
diff --git a/sammy/src/mas/mmas6a.f b/sammy/src/mas/mmas6a.f
index 0a25047ba28f4dc427876e0e2837a11a3abc2cf6..d55ec007f8226a10a6eba0d84766f2cc517a8ca6 100644
--- a/sammy/src/mas/mmas6a.f
+++ b/sammy/src/mas/mmas6a.f
@@ -50,7 +50,7 @@ C ***       True Particle-Pair
 10400          FORMAT ('     Particle a=neutron')
                A = Em1*Aneutr
                WRITE (39,10500) A, Kz1, Spin1
-10500          FORMAT ('     Mb=', F20.10, '     Zb=', I2,
+10500          FORMAT ('     Mb=', F20.15, '     Zb=', I2,
      *            '     Sb=',F5.1)
             ELSE IF (Mt.GT.50 .AND. Mt.LT.99) THEN
 C              Inelastic
@@ -88,7 +88,7 @@ C              Inelastic
             ELSE
                A = Em2*Aneutr
                WRITE (39,11200) A, Kz2, Spin2
-11200          FORMAT ('     Ma=', F20.10, '     Za=', I2,
+11200          FORMAT ('     Ma=', F20.15, '     Za=', I2,
      *            '     Sa=',F5.1)
                A = Em1*Aneutr
                WRITE (39,10500) A, Kz1, Spin1