diff --git a/src/grid/grid3D.h b/src/grid/grid3D.h
index 7b6a7ae59..01635fdf0 100644
--- a/src/grid/grid3D.h
+++ b/src/grid/grid3D.h
@@ -845,13 +845,13 @@ class Grid3D
   void Advance_Particles_KDK_Step2_GPU();
   void Set_Particles_Boundary_GPU(int dir, int side);
   void Set_Particles_Density_Boundaries_Periodic_GPU(int direction, int side);
+  int Load_Particles_Density_Boundary_to_Buffer_GPU(int direction, int side, Real *buffer);
+  void Unload_Particles_Density_Boundary_From_Buffer_GPU(int direction, int side, Real *buffer);
   #endif  // PARTICLES_GPU
   #ifdef GRAVITY_GPU
   void Copy_Potential_From_GPU();
   void Copy_Particles_Density_to_GPU();
   void Copy_Particles_Density_GPU();
-  int Load_Particles_Density_Boundary_to_Buffer_GPU(int direction, int side, Real *buffer);
-  void Unload_Particles_Density_Boundary_From_Buffer_GPU(int direction, int side, Real *buffer);
   #endif  // GRAVITY_GPU
 #endif    // PARTICLES
 
diff --git a/src/particles/density_CIC.cpp b/src/particles/density_CIC.cpp
index 428a0e864..f576aafa4 100644
--- a/src/particles/density_CIC.cpp
+++ b/src/particles/density_CIC.cpp
@@ -70,7 +70,7 @@ void Grid3D::Copy_Particles_Density()
   Copy_Particles_Density_to_GPU();
     #endif
   Copy_Particles_Density_GPU();
-  #else
+  #elif defined(GRAVITY)
 
     #ifndef PARALLEL_OMP
   Copy_Particles_Density_function(0, Grav.nz_local);
@@ -90,11 +90,12 @@ void Grid3D::Copy_Particles_Density()
   }
     #endif  // PARALLEL_OMP
 
-  #endif  // GRAVITY_GPU
+  #endif  // GRAVITY_GPU and GRAVITY
 }
 
 void Grid3D::Copy_Particles_Density_function(int g_start, int g_end)
 {
+  #ifdef GRAVITY
   int nx_part, ny_part, nz_part, nGHST;
   nGHST   = Particles.G.n_ghost_particles_grid;
   nx_part = Particles.G.nx_local + 2 * nGHST;
@@ -116,6 +117,7 @@ void Grid3D::Copy_Particles_Density_function(int g_start, int g_end)
       }
     }
   }
+  #endif  // GRAVITY
 }
 
 // Clear the density array: density=0
diff --git a/src/particles/density_boundaries_gpu.cu b/src/particles/density_boundaries_gpu.cu
index fd5c4ddca..d14069e68 100644
--- a/src/particles/density_boundaries_gpu.cu
+++ b/src/particles/density_boundaries_gpu.cu
@@ -1,9 +1,10 @@
-#if defined(PARTICLES_GPU) && defined(GRAVITY_GPU)
+#if defined(PARTICLES_GPU)
 
   #include <iostream>
 
   #include "../grid/grid3D.h"
   #include "../io/io.h"
+  #include "../utils/error_handling.h"
   #include "particles_3D.h"
 
 __global__ void Set_Particles_Density_Boundaries_Periodic_kernel(int direction, int side, int n_i, int n_j, int nx,
@@ -68,6 +69,9 @@ __global__ void Set_Particles_Density_Boundaries_Periodic_kernel(int direction,
 
 void Grid3D::Set_Particles_Density_Boundaries_Periodic_GPU(int direction, int side)
 {
+    #ifndef GRAVITY_GPU
+  CHOLLA_ERROR("This function should not be invoked when compiled without GPU-Gravity");
+    #endif GRAVITY_GPU
   int n_ghost, nx_g, ny_g, nz_g, size, ngrid, n_i, n_j;
   n_ghost = Particles.G.n_ghost_particles_grid;
   nx_g    = Particles.G.nx_local + 2 * n_ghost;
@@ -148,6 +152,9 @@ __global__ void Load_Particles_Density_Boundary_to_Buffer_kernel(int direction,
 
 int Grid3D::Load_Particles_Density_Boundary_to_Buffer_GPU(int direction, int side, Real *buffer)
 {
+    #ifndef GRAVITY_GPU
+  CHOLLA_ERROR("This function should not be invoked when compiled without GPU-Gravity");
+    #endif GRAVITY_GPU
   int n_ghost, nx_g, ny_g, nz_g, size_buffer, ngrid, n_i, n_j;
   n_ghost = Particles.G.n_ghost_particles_grid;
   nx_g    = Particles.G.nx_local + 2 * n_ghost;
@@ -236,6 +243,9 @@ __global__ void Unload_Particles_Density_Boundary_to_Buffer_kernel(int direction
 
 void Grid3D::Unload_Particles_Density_Boundary_From_Buffer_GPU(int direction, int side, Real *buffer)
 {
+    #ifndef GRAVITY_GPU
+  CHOLLA_ERROR("This function should not be invoked when compiled without GPU-Gravity");
+    #endif GRAVITY_GPU
   int n_ghost, nx_g, ny_g, nz_g, size_buffer, ngrid, n_i, n_j;
   n_ghost = Particles.G.n_ghost_particles_grid;
   nx_g    = Particles.G.nx_local + 2 * n_ghost;
@@ -276,4 +286,4 @@ void Grid3D::Unload_Particles_Density_Boundary_From_Buffer_GPU(int direction, in
 
   #endif  // MPI_CHOLLA
 
-#endif  // PARTICLES_GPU & GRAVITY_GPU
+#endif  // PARTICLES_GPU
diff --git a/src/particles/gravity_CIC.cpp b/src/particles/gravity_CIC.cpp
index 495e7cf33..c6bc5368d 100644
--- a/src/particles/gravity_CIC.cpp
+++ b/src/particles/gravity_CIC.cpp
@@ -46,7 +46,7 @@ void Grid3D::Get_Gravity_Field_Particles()
     #endif  // PARALLEL_OMP
   #endif    // PARTICLES_CPU
 
-  #ifdef PARTICLES_GPU
+  #if defined(PARTICLES_GPU) && defined(GRAVITY_GPU)
   Particles.Get_Gravity_Field_Particles_GPU(Grav.F.potential_h);
   #endif
 }
diff --git a/src/particles/gravity_CIC_gpu.cu b/src/particles/gravity_CIC_gpu.cu
index 4711b1a32..62e30555f 100644
--- a/src/particles/gravity_CIC_gpu.cu
+++ b/src/particles/gravity_CIC_gpu.cu
@@ -108,9 +108,10 @@ void Particles3D::Get_Gravity_Field_Particles_GPU_function(int nx_local, int ny_
                                                            Real *gravity_x_dev, Real *gravity_y_dev,
                                                            Real *gravity_z_dev)
 {
-    #ifndef GRAVITY_GPU
+    #ifdef GRAVITY
+      #ifndef GRAVITY_GPU
   Copy_Potential_To_GPU(potential_host, potential_dev, n_cells_potential);
-    #endif
+      #endif
 
   int nx_g, ny_g, nz_g;
   nx_g = nx_local + 2 * N_GHOST_POTENTIAL;
@@ -133,6 +134,7 @@ void Particles3D::Get_Gravity_Field_Particles_GPU_function(int nx_local, int ny_
                      gravity_y_dev, gravity_z_dev, nx_local, ny_local, nz_local, n_ghost_particles_grid,
                      N_GHOST_POTENTIAL, dx, dy, dz);
   GPU_Error_Check();
+    #endif  // GRAVITY
 }
 
 // Get CIC indexes from the particles positions
diff --git a/src/particles/particles_3D.h b/src/particles/particles_3D.h
index dbda79be5..d64e35e34 100644
--- a/src/particles/particles_3D.h
+++ b/src/particles/particles_3D.h
@@ -17,6 +17,8 @@
     #include "../grid/spatial_domain_props.h"
 
     #ifdef PARTICLES_GPU
+      #include "../utils/gpu.hpp" // cudaFree
+
       #define TPB_PARTICLES 1024
       // #define PRINT_GPU_MEMORY
       #define PRINT_MAX_MEMORY_USAGE
diff --git a/src/particles/particles_boundaries.cpp b/src/particles/particles_boundaries.cpp
index 96e4f110e..5310a847d 100644
--- a/src/particles/particles_boundaries.cpp
+++ b/src/particles/particles_boundaries.cpp
@@ -96,9 +96,11 @@ void Grid3D::Unload_Particles_From_Buffers_BLOCK(int index, int *flags)
   if (H.TRANSFER_HYDRO_BOUNDARIES) {
     return;
   }
+  #ifdef GRAVITY
   if (Grav.TRANSFER_POTENTIAL_BOUNDARIES) {
     return;
   }
+  #endif
 
   if (index == 0) {
     Unload_Particles_from_Buffer_X0(flags);