diff --git a/src/f77/CMakeLists.txt b/src/f77/CMakeLists.txt
index a76a5e4bf..ccef9639d 100644
--- a/src/f77/CMakeLists.txt
+++ b/src/f77/CMakeLists.txt
@@ -21,6 +21,11 @@ IF( CMAKE_COMPILER_IS_GNUCC )
         MESSAGE( STATUS "adding -fno-range-check fortran compiler flag" )
         SET( CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fno-range-check" )
     ENDIF()
+    IF ( ${GCC_VERSION} VERSION_GREATER 10 )
+      # fix the BOZ literal constant errors that are treated more stringent
+      # starting from gcc10 (turns the errors into warnings)
+      SET(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fallow-invalid-boz")
+    ENDIF()
 ENDIF()
 
 
diff --git a/src/f77/simjob.F b/src/f77/simjob.F
index 6864d6c7f..426e47c56 100644
--- a/src/f77/simjob.F
+++ b/src/f77/simjob.F
@@ -314,7 +314,7 @@ subroutine my_simjob
               status     = lctphsetcellid( tpcHit, j-1 )
               status     = lctphsettime( tpcHit, 0.1234567 )
               status     = lctphsetcharge( tpcHit, 3.14159 )
-              status     = lctphsetquality( tpcHit, z'bad' )
+              status     = lctphsetquality( tpcHit, int(z'bad') )
               if (storeRawData)  then
                 size       = ( dble(irand( 0 ) )/RAND_MAX )*10
                 do  k = 1,size
diff --git a/src/f77/simjob_chain.F b/src/f77/simjob_chain.F
index f8d23186c..81cb3df76 100644
--- a/src/f77/simjob_chain.F
+++ b/src/f77/simjob_chain.F
@@ -190,7 +190,7 @@ subroutine simjob ( ipass, filename )                         !*
 c------   simulated tracker hits
 
 c--------   set the flag bits to store position and pdg for simulated calorimeter hits
-            flag = 2**31 + 2**28
+            flag = (-2)**31 + 2**28
             status = lccolsetflag( schcol, flag )
 
             do k=1,nhit
@@ -239,7 +239,7 @@ subroutine simjob ( ipass, filename )                         !*
 c---- real data calorimeter hits
 
 c ----      set the flag bits to store position for calorimeter hits
-            flag = 2**31
+            flag = (-2)**31
             status = lccolsetflag( cahcol, flag )
 
             do k=1,nhit