diff --git a/opencl_fdtd/kernels/update_e.cl b/opencl_fdtd/kernels/update_e.cl
index 63a0c6f..eed4ee5 100644
--- a/opencl_fdtd/kernels/update_e.cl
+++ b/opencl_fdtd/kernels/update_e.cl
@@ -50,7 +50,7 @@ ftype pEzi = 0;
         {%- set se, sh = '+', '-' -%}
     {%- endif -%}
 
-pml_{{r ~ p}}_thickness = {{pml['thickness']}};
+int pml_{{r ~ p}}_thickness = {{pml['thickness']}};
 
     {%- if p == 'n' %}
 
diff --git a/opencl_fdtd/kernels/update_h.cl b/opencl_fdtd/kernels/update_h.cl
index cdda3a9..27d7a47 100644
--- a/opencl_fdtd/kernels/update_h.cl
+++ b/opencl_fdtd/kernels/update_h.cl
@@ -64,7 +64,7 @@ ftype pHzi = 0;
         {%- set se, sh = '+', '-' -%}
     {%- endif -%}
 
-pml_{{r ~ p}}_thickness = {{pml['thickness']}};
+int pml_{{r ~ p}}_thickness = {{pml['thickness']}};
 
     {%- if p == 'n' %}