diff --git a/Source/Utils/WarpXTagging.cpp b/Source/Utils/WarpXTagging.cpp
index 2a404b5985c..807c92b2f0b 100644
--- a/Source/Utils/WarpXTagging.cpp
+++ b/Source/Utils/WarpXTagging.cpp
@@ -31,8 +31,10 @@ WarpX::ErrorEst (int lev, TagBoxArray& tags, Real /*time*/, int /*ngrow*/)
     const auto problo = Geom(lev).ProbLoArray();
     const auto dx = Geom(lev).CellSizeArray();
 
-    amrex::ParserExecutor<3> const& ref_parser = ref_patch_parser->compile<3>();
-
+    amrex::ParserExecutor<3> ref_parser;
+    if (ref_patch_parser) ref_parser = ref_patch_parser->compile<3>();
+    const auto ftlo = fine_tag_lo;
+    const auto fthi = fine_tag_hi;
 #ifdef AMREX_USE_OMP
 #pragma omp parallel if (amrex::Gpu::notInLaunchRegion())
 #endif
@@ -45,15 +47,20 @@ WarpX::ErrorEst (int lev, TagBoxArray& tags, Real /*time*/, int /*ngrow*/)
             const RealVect pos {AMREX_D_DECL((i+0.5_rt)*dx[0]+problo[0],
                                        (j+0.5_rt)*dx[1]+problo[1],
                                        (k+0.5_rt)*dx[2]+problo[2])};
+            bool tag_val = 0;
+            if (ref_parser) {
 #if defined (WARPX_DIM_3D)
-            amrex::Real tag_val = ref_parser(pos[0], pos[1], pos[2]);
+                tag_val = (ref_parser(pos[0], pos[1], pos[2]) == 1);
 #elif defined (WARPX_DIM_XZ) || defined (WARPX_DIM_RZ)
-            amrex::Real unused = 0.0;
-            amrex::Real tag_val = ref_parser(pos[0], unused, pos[1]);
+                amrex::Real unused = 0.0;
+                tag_val = (ref_parser(pos[0], unused, pos[1]) == 1);
 #elif defined (WARPX_DIM_1D_Z)
-            amrex::Real unused = 0.0;
-            amrex::Real tag_val = ref_parser(unused, unused, pos[0]);
+                amrex::Real unused = 0.0;
+                tag_val = (ref_parser(unused, unused, pos[0]) == 1);
 #endif
+            } else {
+                tag_val = (pos > ftlo && pos < fthi);
+            }
             if ( tag_val == 1) {
                 fab(i,j,k) = TagBox::SET;
             }
diff --git a/Source/WarpX.cpp b/Source/WarpX.cpp
index d0403b95b60..96cf5edee7d 100644
--- a/Source/WarpX.cpp
+++ b/Source/WarpX.cpp
@@ -1006,34 +1006,11 @@ WarpX::ReadParameters ()
             if (fine_tag_lo_specified && fine_tag_hi_specified) {
                 fine_tag_lo = RealVect{lo};
                 fine_tag_hi = RealVect{hi};
-#if defined (WARPX_DIM_3D)
-                ref_patch_function =   " ( x > " + std::to_string(fine_tag_lo[0]) + " ) "
-                                   + " * ( x < " + std::to_string(fine_tag_hi[0]) + " )"
-                                   + " * ( y > " + std::to_string(fine_tag_lo[1]) + " )"
-                                   + " * ( y < " + std::to_string(fine_tag_hi[1]) + " )"
-                                   + " * ( z > " + std::to_string(fine_tag_lo[2]) + " )"
-                                   + " * ( z < " + std::to_string(fine_tag_hi[2]) + " )";
-#elif defined (WARPX_DIM_RZ)
-                ref_patch_function =   " ( x > " + std::to_string(fine_tag_lo[0]) + " ) "
-                                   + " * ( x < " + std::to_string(fine_tag_hi[0]) + " )"
-                                   + " * ( z > " + std::to_string(fine_tag_lo[1]) + " )"
-                                   + " * ( z < " + std::to_string(fine_tag_hi[1]) + " )";
-#elif defined (WARPX_DIM_XZ)
-                ref_patch_function =   " ( x > " + std::to_string(fine_tag_lo[0]) + " ) "
-                                   + " * ( x < " + std::to_string(fine_tag_hi[0]) + " )"
-                                   + " * ( z > " + std::to_string(fine_tag_lo[1]) + " )"
-                                   + " * ( z < " + std::to_string(fine_tag_hi[1]) + " )";
-#elif defined (WARPX_DIM_1D_Z)
-                ref_patch_function =   " ( z > " + std::to_string(fine_tag_lo[0]) + " ) "
-                                   + " * ( z < " + std::to_string(fine_tag_hi[0]) + " )";
-#endif
-                amrex::Print() << " ref patch func " << ref_patch_function << "\n";
             } else {
-                utils::parser::Store_parserString(pp_warpx, "ref_patch_function(x,y,z)",
-                    ref_patch_function);
+                utils::parser::Store_parserString(pp_warpx, "ref_patch_function(x,y,z)", ref_patch_function);
+                ref_patch_parser = std::make_unique<amrex::Parser>(
+                    utils::parser::makeParser(ref_patch_function,{"x","y","z"}));
             }
-            ref_patch_parser = std::make_unique<amrex::Parser>(
-                utils::parser::makeParser(ref_patch_function,{"x","y","z"}));
         }
 
         pp_warpx.query("do_dynamic_scheduling", do_dynamic_scheduling);