diff --git a/cmake/Modules/Packages/USER-PACE.cmake b/cmake/Modules/Packages/USER-PACE.cmake
index b953278e75..e8262f7d40 100644
--- a/cmake/Modules/Packages/USER-PACE.cmake
+++ b/cmake/Modules/Packages/USER-PACE.cmake
@@ -1,6 +1,6 @@
 
-set(PACELIB_URL "https://github.com/ICAMS/lammps-user-pace/archive/refs/tags/v.2021.2.3.upd.tar.gz" CACHE STRING "URL for PACE evaluator library sources")
-set(PACELIB_MD5 "8041e3de7254815eb3ff0a11e2cc84ea" CACHE STRING "MD5 checksum of PACE evaluator library tarball")
+set(PACELIB_URL "https://github.com/ICAMS/lammps-user-pace/archive/refs/tags/v.2021.2.3.upd2.tar.gz" CACHE STRING "URL for PACE evaluator library sources")
+set(PACELIB_MD5 "8fd1162724d349b930e474927197f20d" CACHE STRING "MD5 checksum of PACE evaluator library tarball")
 mark_as_advanced(PACELIB_URL)
 mark_as_advanced(PACELIB_MD5)
 
diff --git a/lib/pace/Install.py b/lib/pace/Install.py
index 5f72157611..91aa8b3a46 100644
--- a/lib/pace/Install.py
+++ b/lib/pace/Install.py
@@ -18,11 +18,11 @@ parser = ArgumentParser(prog='Install.py',
 # settings
 
 thisdir = fullpath('.')
-version = "v.2021.2.3.upd"
+version = "v.2021.2.3.upd2"
 
 # known checksums for different PACE versions. used to validate the download.
 checksums = { \
-        'v.2021.2.3.upd' : '8041e3de7254815eb3ff0a11e2cc84ea', \
+        'v.2021.2.3.upd2' : '8fd1162724d349b930e474927197f20d', \
         }
 
 
diff --git a/lib/pace/Makefile b/lib/pace/Makefile
index baaef0b837..c2e1892ddd 100644
--- a/lib/pace/Makefile
+++ b/lib/pace/Makefile
@@ -12,11 +12,10 @@ OBJ =   $(SRC:.cpp=.o)
 
 
 # ------ SETTINGS ------
-CXXFLAGS = -O2 -fPIC -Isrc/USER-PACE
+CXXFLAGS = -O3 -fPIC -Isrc/USER-PACE
 
 ARCHIVE =	ar
 ARCHFLAG =	-rc
-DEPFLAGS =  -M
 USRLIB =
 SYSLIB =
 
@@ -35,4 +34,4 @@ clean-all:
 	-rm -f *~ $(OBJ) $(LIB)
 
 clean-build:
-	-rm -f *~ $(OBJ)
\ No newline at end of file
+	-rm -f *~ $(OBJ)