diff --git a/src/settings.F90 b/src/settings.F90
index dfe4afbe3..710a87e1e 100644
--- a/src/settings.F90
+++ b/src/settings.F90
@@ -121,7 +121,6 @@ module settings
   character(MAX_FILE_LEN) :: path_input               ! Path to input file
   character(MAX_FILE_LEN) :: path_cross_sections = '' ! Path to cross_sections.xml
   character(MAX_FILE_LEN) :: path_multipole           ! Path to wmp library
-  character(MAX_FILE_LEN) :: path_source = ''         ! Path to binary source
   character(MAX_FILE_LEN) :: path_state_point         ! Path to binary state point
   character(MAX_FILE_LEN) :: path_source_point        ! Path to binary source point
   character(MAX_FILE_LEN) :: path_particle_restart    ! Path to particle restart
diff --git a/src/simulation.F90 b/src/simulation.F90
index b5d24180c..d5ca165b5 100644
--- a/src/simulation.F90
+++ b/src/simulation.F90
@@ -253,7 +253,10 @@ contains
 
   subroutine finalize_generation()
 
-    integer(8) :: i
+    interface
+      subroutine fill_source_bank_fixedsource() bind(C)
+      end subroutine
+    end interface
 
     ! Update global tallies with the omp private accumulation variables
 !$omp parallel
@@ -306,13 +309,7 @@ contains
 
     elseif (run_mode == MODE_FIXEDSOURCE) then
       ! For fixed-source mode, we need to sample the external source
-      if (path_source == '') then
-        do i = 1, work
-          call set_particle_seed((total_gen + overall_generation()) * &
-               n_particles + work_index(rank) + i)
-          source_bank(i) = sample_external_source()
-        end do
-      end if
+      call fill_source_bank_fixedsource()
     end if
 
   end subroutine finalize_generation
diff --git a/src/simulation_header.F90 b/src/simulation_header.F90
index 7addf9b2c..d7040b8d5 100644
--- a/src/simulation_header.F90
+++ b/src/simulation_header.F90
@@ -80,8 +80,8 @@ contains
 ! OVERALL_GENERATION determines the overall generation number
 !===============================================================================
 
-  pure function overall_generation() result(gen)
-    integer :: gen
+  pure function overall_generation() result(gen) bind(C)
+    integer(C_INT) :: gen
     gen = gen_per_batch*(current_batch - 1) + current_gen
   end function overall_generation
 
diff --git a/src/source.cpp b/src/source.cpp
index e01c9795e..c3869fcf4 100644
--- a/src/source.cpp
+++ b/src/source.cpp
@@ -352,4 +352,28 @@ extern "C" double total_source_strength()
   return strength;
 }
 
+// Needed in fill_source_bank_fixedsource
+extern "C" int overall_generation();
+
+//! Fill source bank at end of generation for fixed source simulations
+extern "C" void fill_source_bank_fixedsource()
+{
+  if (path_source.empty()) {
+    // Get pointer to source bank
+    Bank* source_bank;
+    int64_t n;
+    openmc_source_bank(&source_bank, &n);
+
+    for (int64_t i = 0; i < openmc_work; ++i) {
+      // initialize random number seed
+      int64_t id = (openmc_total_gen + overall_generation())*n_particles +
+        work_index[openmc::mpi::rank] + i + 1;
+      set_particle_seed(id);
+
+      // sample external source distribution
+      source_bank[i] = sample_external_source();
+    }
+  }
+}
+
 } // namespace openmc