diff --git a/openpmd_viewer/openpmd_timeseries/main.py b/openpmd_viewer/openpmd_timeseries/main.py
index 42458d21..ac65ad1c 100644
--- a/openpmd_viewer/openpmd_timeseries/main.py
+++ b/openpmd_viewer/openpmd_timeseries/main.py
@@ -139,7 +139,7 @@ def get_particle(self, var_list=None, species=None, t=None, iteration=None,
 
         Parameters
         ----------
-        var_list : list of string, optional
+        var_list : list of string
             A list of the particle variables to extract. If var_list is not
             provided, the available particle quantities are printed
 
@@ -278,8 +278,8 @@ def get_particle(self, var_list=None, species=None, t=None, iteration=None,
             data_list = apply_selection( iteration, self.data_reader,
                 data_list, select, species, self.extensions)
         elif isinstance( select, ParticleTracker ):
-            data_list = select.extract_tracked_particles( iteration,
-                self.data_reader, data_list, species, self.extensions )
+            data_list = select.extract_tracked_particles(iteration,
+                self.data_reader, data_list, var_list, species, self.extensions)
 
         # Plotting
         if plot and len(var_list) in [1, 2]:
diff --git a/openpmd_viewer/openpmd_timeseries/particle_tracker.py b/openpmd_viewer/openpmd_timeseries/particle_tracker.py
index b51e6d98..8ad09731 100644
--- a/openpmd_viewer/openpmd_timeseries/particle_tracker.py
+++ b/openpmd_viewer/openpmd_timeseries/particle_tracker.py
@@ -106,7 +106,7 @@ def __init__(self, ts, species=None, t=None,
 
 
     def extract_tracked_particles( self, iteration, data_reader, data_list,
-                                    species, extensions ):
+                                    var_list, species, extensions ):
         """
         Select the elements of each particle quantities in data_list,
         so as to only return those that correspond to the tracked particles
@@ -123,6 +123,9 @@ def extract_tracked_particles( self, iteration, data_reader, data_list,
             A list of arrays with one element per macroparticle, that represent
             different particle quantities
 
+        var_list: list of string
+            The list of variable names that corresponds to `data_list`
+
         species: string
             Name of the species being requested
 
@@ -144,11 +147,11 @@ def extract_tracked_particles( self, iteration, data_reader, data_list,
         for i in range(len(data_list)):
             if len(data_list[i]) > 1:  # Do not apply selection on scalars
                 data_list[i] = self.extract_quantity(
-                    data_list[i], selected_indices )
+                    data_list[i], var_list[i], selected_indices )
 
         return( data_list )
 
-    def extract_quantity( self, q, selected_indices ):
+    def extract_quantity( self, q, name, selected_indices ):
         """
         Select the elements of the array `q`, so as to only return those
         that correspond to the tracked particles.
@@ -158,6 +161,9 @@ def extract_quantity( self, q, selected_indices ):
         q: 1d array of floats or ints
             A particle quantity (one element per particle)
 
+        name: string
+            Name of the particle quantity `q`
+
         selected_indices: 1d array of ints
             The indices (in array q) of the particles to be selected.
             If `preserve_particle_index` was selected to be True, this array
@@ -174,14 +180,12 @@ def extract_quantity( self, q, selected_indices ):
 
         # Handle the absent particles
         if self.preserve_particle_index:
-            if q.dtype in [ np.float64, np.float32 ]:
+            if name == 'id':
+                selected_q = self.selected_pid
+            else:
                 # Fill the position of absent particles by NaNs
                 selected_q = np.where( selected_indices == -1,
                                         np.nan, selected_q)
-            else:
-                # The only non-float quantity in openPMD-viewer is particle id
-                selected_q = self.selected_pid
-
         return( selected_q )
 
     def get_extraction_indices( self, pid ):