diff --git a/CMakeLists.txt b/CMakeLists.txt
index a8b801eb75..41ca8d8eec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -270,7 +270,7 @@ endif()
 # Show flags being used
 message(STATUS "Fortran flags: ${f90flags}")
 message(STATUS "C flags: ${cflags}")
-message(STATUS "CXX flags: ${cxxflags}")
+message(STATUS "C++ flags: ${cxxflags}")
 message(STATUS "Linker flags: ${ldflags}")
 
 #===============================================================================
diff --git a/src/constants.F90 b/src/constants.F90
index 73aca25d29..2466dbb145 100644
--- a/src/constants.F90
+++ b/src/constants.F90
@@ -1,5 +1,7 @@
 module constants
 
+  use, intrinsic :: ISO_C_BINDING
+
   implicit none
 
   ! ============================================================================
@@ -419,6 +421,7 @@ module constants
   integer, parameter :: STREAM_SOURCE     = 3
   integer, parameter :: STREAM_URR_PTABLE = 4
   integer, parameter :: STREAM_VOLUME     = 5
+  integer(C_INT64_T), parameter :: DEFAULT_SEED = 1_8
 
   ! ============================================================================
   ! MISCELLANEOUS CONSTANTS
diff --git a/src/initialize.F90 b/src/initialize.F90
index 117381328e..21d568c72a 100644
--- a/src/initialize.F90
+++ b/src/initialize.F90
@@ -20,7 +20,7 @@ module initialize
   use message_passing
   use mgxs_data,       only: read_mgxs, create_macro_xs
   use output,          only: print_version, write_message, print_usage
-  use random_lcg,      only: openmc_set_seed, seed
+  use random_lcg,      only: openmc_set_seed
   use settings
 #ifdef _OPENMP
   use simulation_header, only: n_threads
@@ -84,7 +84,7 @@ contains
 
     ! Initialize random number generator -- if the user specifies a seed, it
     ! will be re-initialized later
-    err = openmc_set_seed(seed)
+    err = openmc_set_seed(DEFAULT_SEED)
 
     ! Read XML input files
     call read_input_xml()
diff --git a/src/random_lcg.C b/src/random_lcg.C
index ef49cd13b4..5bdf13d708 100644
--- a/src/random_lcg.C
+++ b/src/random_lcg.C
@@ -15,11 +15,11 @@ const double   prn_norm   = pow(2, -63);             // 2^-63
 
 // Module constants
 const int N_STREAMS         = 5;
-const int STREAM_TRACKING   = 0;
-const int STREAM_TALLIES    = 1;
-const int STREAM_SOURCE     = 2;
-const int STREAM_URR_PTABLE = 3;
-const int STREAM_VOLUME     = 4;
+const int STREAM_TRACKING   = 1;
+const int STREAM_TALLIES    = 2;
+const int STREAM_SOURCE     = 3;
+const int STREAM_URR_PTABLE = 4;
+const int STREAM_VOLUME     = 5;
 
 // Current PRNG state
 uint64_t prn_seed[N_STREAMS];  // current seed
@@ -48,9 +48,9 @@ prn()
 //==============================================================================
 
 extern "C" double
-future_prn(uint64_t n)
+future_prn(int64_t n)
 {
-  return future_seed(n, prn_seed[stream]) * prn_norm;
+  return future_seed(static_cast<uint64_t>(n), prn_seed[stream]) * prn_norm;
 }
 
 //==============================================================================
@@ -58,10 +58,10 @@ future_prn(uint64_t n)
 //==============================================================================
 
 extern "C" void
-set_particle_seed(uint64_t id)
+set_particle_seed(int64_t id)
 {
   for (int i = 0; i < N_STREAMS; i++) {
-    prn_seed[i] = future_seed(id * prn_stride, seed + i);
+    prn_seed[i] = future_seed(static_cast<uint64_t>(id) * prn_stride, seed + i);
   }
 }
 
@@ -70,16 +70,16 @@ set_particle_seed(uint64_t id)
 //==============================================================================
 
 extern "C" void
-advance_prn_seed(uint64_t n)
+advance_prn_seed(int64_t n)
 {
-  prn_seed[stream] = future_seed(n, prn_seed[stream]);
+  prn_seed[stream] = future_seed(static_cast<uint64_t>(n), prn_seed[stream]);
 }
 
 //==============================================================================
 // FUTURE_SEED
 //==============================================================================
 
-extern "C" uint64_t
+uint64_t
 future_seed(uint64_t n, uint64_t seed)
 {
   // Make sure nskip is less than 2^M.
@@ -121,7 +121,7 @@ future_seed(uint64_t n, uint64_t seed)
 extern "C" void
 prn_set_stream(int i)
 {
-  stream = i - 1;
+  stream = i - 1;  // Shift by one to move from Fortran to C indexing.
 }
 
 //==============================================================================
@@ -136,7 +136,7 @@ openmc_set_seed(uint64_t new_seed)
   for (int i = 0; i < N_STREAMS; i++) {
     prn_seed[i] = seed + i;
   }
-  stream = STREAM_TRACKING;
+  prn_set_stream(STREAM_TRACKING);
 #pragma end omp parallel
   return 0;
 }
diff --git a/src/random_lcg.h b/src/random_lcg.h
index 889195f109..4c7ec01404 100644
--- a/src/random_lcg.h
+++ b/src/random_lcg.h
@@ -14,21 +14,21 @@ extern "C" double prn();
 // current seed.
 //==============================================================================
 
-extern "C" double future_prn(uint64_t n);
+extern "C" double future_prn(int64_t n);
 
 //==============================================================================
 // SET_PARTICLE_SEED sets the seed to a unique value based on the ID of the
 // particle.
 //==============================================================================
 
-extern "C" void set_particle_seed(uint64_t id);
+extern "C" void set_particle_seed(int64_t id);
 
 //==============================================================================
 // ADVANCE_PRN_SEED advances the random number seed 'n' times from the current
 // seed.
 //==============================================================================
 
-extern "C" void advance_prn_seed(uint64_t n);
+extern "C" void advance_prn_seed(int64_t n);
 
 //==============================================================================
 // FUTURE_SEED advances the random number seed 'skip' times. This is usually
@@ -37,7 +37,7 @@ extern "C" void advance_prn_seed(uint64_t n);
 // are used.
 //==============================================================================
 
-extern "C" uint64_t future_seed(uint64_t n, uint64_t seed);
+uint64_t future_seed(uint64_t n, uint64_t seed);
 
 //==============================================================================
 // PRN_SET_STREAM changes the random number stream. If random numbers are needed