diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 19bb45bb3..8eb1d2d42 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -67,7 +67,7 @@ simulation_stack:
 .spack_nmodl:
   variables:
     SPACK_PACKAGE: nmodl
-    SPACK_PACKAGE_SPEC: ~legacy-unit+python
+    SPACK_PACKAGE_SPEC: +python
 
 spack_setup:
   extends: .spack_setup_ccache
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 20573097a..9a9883983 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,11 +18,7 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 # Build options for NMODL
 # =============================================================================
 option(NMODL_ENABLE_PYTHON_BINDINGS "Enable pybind11 based python bindings" ON)
-option(NMODL_ENABLE_LEGACY_UNITS "Use original faraday, R, etc. instead of 2019 nist constants" OFF)
 option(NMODL_ENABLE_TESTS "Enable build of tests" ON)
-if(NMODL_ENABLE_LEGACY_UNITS)
-  add_definitions(-DUSE_LEGACY_UNITS)
-endif()
 set(NMODL_EXTRA_CXX_FLAGS
     ""
     CACHE STRING "Add extra compile flags for NMODL sources")
@@ -220,21 +216,10 @@ include(${PROJECT_SOURCE_DIR}/src/language/code_generator.cmake)
 
 add_subdirectory(src)
 
-# =============================================================================
-# Prepare units database file from nrnunits.lib.in
-# =============================================================================
-if(NMODL_ENABLE_LEGACY_UNITS)
-  set(LegacyY "")
-  set(LegacyN "/")
-else()
-  set(LegacyY "/")
-  set(LegacyN "")
-endif()
-configure_file(share/nrnunits.lib.in ${CMAKE_CURRENT_BINARY_DIR}/share/nmodl/nrnunits.lib @ONLY)
-
 # =============================================================================
 # Install unit database to share
 # =============================================================================
+configure_file(share/nrnunits.lib ${CMAKE_CURRENT_BINARY_DIR}/share/nmodl/nrnunits.lib COPYONLY)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/share/nmodl/nrnunits.lib
         DESTINATION ${NMODL_INSTALL_DIR_SUFFIX}share/nmodl)
 
@@ -268,7 +253,6 @@ message(STATUS "--------------------+-------------------------------------------
 message(STATUS "CXX COMPILER        | ${CMAKE_CXX_COMPILER}")
 message(STATUS "COMPILE FLAGS       | ${COMPILER_FLAGS}")
 message(STATUS "Build Type          | ${CMAKE_BUILD_TYPE}")
-message(STATUS "Legacy Units        | ${NMODL_ENABLE_LEGACY_UNITS}")
 message(STATUS "Python Bindings     | ${NMODL_ENABLE_PYTHON_BINDINGS}")
 message(STATUS "Flex                | ${FLEX_EXECUTABLE}")
 message(STATUS "Bison               | ${BISON_EXECUTABLE}")
diff --git a/share/nrnunits.lib.in b/share/nrnunits.lib
similarity index 95%
rename from share/nrnunits.lib.in
rename to share/nrnunits.lib
index 8af235ee5..8fb81e7f5 100755
--- a/share/nrnunits.lib.in
+++ b/share/nrnunits.lib
@@ -68,15 +68,13 @@ pi			3.14159265358979323846
 c			2.99792458+8 m/sec fuzz
 g			9.80665 m/sec2
 au			1.49597871+11 m fuzz
-@LegacyY@mole			6.022169+23 fuzz
-@LegacyN@mole			6.02214076+23 fuzz
+mole			6.02214076+23 fuzz
 mol             1
 / mol is explicitly defined as a constant
 / with value 1 to avoid "undefined unit"
 / error with mod files that don't define
 / it themselves
-@LegacyY@e			1.6021917-19 coul fuzz
-@LegacyN@e			1.602176634-19 coul fuzz
+e			1.602176634-19 coul fuzz
 energy			c2
 force			g
 mercury			1.33322+5 kg/m2-sec2
@@ -399,8 +397,7 @@ ev			e-volt
 / faraday			9.652000+04 coul
 / faraday  from  host: physics.nist.gov
 /          	 path: /PhysRefData/fundconst/html/keywords.html
-@LegacyY@faraday		9.6485309+4 coul
-@LegacyN@faraday		e-mole
+faraday		e-mole
 fathom			6 ft
 fermi			1-15 m
 fifth			4|5 qt
@@ -436,8 +433,7 @@ hyl			gm force sec2/m
 hz			/sec
 imaginarycubicfoot	1.4 ft3
 jeroboam		4|5 gal
-@LegacyY@boltzmann		1.38064852-23 joule/K
-@LegacyN@boltzmann		1.380649-23 joule/K
+boltzmann		1.380649-23 joule/K
 k			boltzmann
 karat			1|24
 kcal			kilocal
@@ -506,8 +502,7 @@ quarter			9 in
 quartersection		1|4 mi2
 quintal			100 kg
 quire			25
-@LegacyY@gasconstant		8.3144598 joule/K
-@LegacyN@gasconstant		k-mole
+gasconstant		k-mole
 R			gasconstant
 rad			100 erg/gm
 ream			500
@@ -581,10 +576,8 @@ tex			.001 gram / m
 englishell		45 inch
 scottishell		37.2 inch
 flemishell		27 inch
-@LegacyY@planck			6.626-34 joule-sec
-@LegacyN@planck			6.62607015-34 joule-sec
-@LegacyY@hbar			1.055-34 joule-sec
-@LegacyN@hbar			planck/two-pi
+planck			6.62607015-34 joule-sec
+hbar			planck/two-pi
 electronmass		9.1095-31 kg
 protonmass		1.6726-27 kg
 neutronmass		1.6606-27 kg
diff --git a/src/visitors/units_visitor.cpp b/src/visitors/units_visitor.cpp
index 0da2a1c6c..2ad612d0e 100644
--- a/src/visitors/units_visitor.cpp
+++ b/src/visitors/units_visitor.cpp
@@ -128,13 +128,7 @@ void UnitsVisitor::visit_factor_def(ast::FactorDef& node) {
         auto node_unit_name = node.get_node_name();
         auto unit1_factor = units_driver.table->get_unit(node_unit_name + "_unit1")->get_factor();
         auto unit2_factor = units_driver.table->get_unit(node_unit_name + "_unit2")->get_factor();
-
-#ifdef USE_LEGACY_UNITS
-        auto unit_factor = stringutils::to_string(unit1_factor / unit2_factor, "{:g}");
-#else
         auto unit_factor = stringutils::to_string(unit1_factor / unit2_factor, "{:a}");
-#endif
-
         auto double_value_ptr = std::make_shared<ast::Double>(ast::Double(unit_factor));
         node.set_value(std::move(double_value_ptr));
     }