diff --git a/CMakeLists.txt b/CMakeLists.txt
index 95ec804617..2e52f56a0b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -133,6 +133,27 @@ IF(${BIGENDIAN})
   SET(WORDS_BIGENDIAN "1")
 ENDIF(${BIGENDIAN})
 
+# Define a function to convert various true or false values
+# to either TRUE|FALSE (uppercase).
+# If value is not a recognized boolean, then return NOTFOUND
+#1, ON, YES, TRUE, Y, 
+#0, OFF, NO, FALSE, N, IGNORE, NOTFOUND -NOTFOUND ""
+
+SET(TRUELIST "on;yes;y;true")
+SET(FALSELIST "off;no;n;false;0;ignore;notfound")
+function(booleanize VALUE RETVAR)
+  # force case
+  STRING(TOLOWER "${VALUE}" LCVALUE)
+  # Now do all the comparisons
+  if(LCVALUE IN_LIST TRUELIST OR LCVALUE GREATER 0)
+    SET(${RETVAR} TRUE PARENT_SCOPE)
+  elseif(LCVALUE IN_LIST FALSELIST OR LCVALUE MATCHES ".*-notfound" OR LCVALUE STREQUAL "")
+    SET(${RETVAR} FALSE PARENT_SCOPE)
+   else()
+     SET(${RETVAR} NOTFOUND PARENT_SCOPE)
+  endif()
+endfunction()
+
 # A macro to check if a C linker supports a particular flag.
 MACRO(CHECK_C_LINKER_FLAG M_FLAG M_RESULT)
   SET(T_REQ_FLAG "${CMAKE_REQUIRED_FLAGS}")
@@ -1120,41 +1141,60 @@ ENDIF()
 
 # If user wants, then install selected plugins (default on)
 SET(PLUGIN_INSTALL_DIR "NO" CACHE STRING "Whether and where we should install plugins; defaults to yes")
-SET(ENABLE_PLUGIN_INSTALL NO)
-IF(DEFINED PLUGIN_INSTALL_DIR) #OR DEFINED CACHE{PLUGIN_INSTALL_DIR}
-  STRING(TOLOWER "${PLUGIN_INSTALL_DIR}" LCPID)
-  IF(LCPID STREQUAL "no")
-    SET(ENABLE_PLUGIN_INSTALL NO)
-  ELSE()
+
+# This is ugly, but seems necessary because of CMake's boolean structure
+SET(boolval FALSE)
+IF(DEFINED PLUGIN_INSTALL_DIR)
+  booleanize(${PLUGIN_INSTALL_DIR} boolval)
+  IF(boolval)
     SET(ENABLE_PLUGIN_INSTALL YES)
+    # No actual value was specified
+    UNSET(PLUGIN_INSTALL_DIR CACHE)
+  ELSE()
+    IF(boolval STREQUAL "NOTFOUND")
+      # Must be an actual value
+      SET(ENABLE_PLUGIN_INSTALL YES)
+    ELSE()
+      SET(ENABLE_PLUGIN_INSTALL NO)
+    ENDIF()
   ENDIF()
+ELSE()
+  SET(ENABLE_PLUGIN_INSTALL NO)
 ENDIF()
 
-IF(ENABLE_PLUGIN_INSTALL AND PLUGIN_INSTALL_DIR STREQUAL "YES")
-    # Default to last dir (lowest search priority) in HDF5_PLUGIN_PATH
-    IF(DEFINED ENV{HDF5_PLUGIN_PATH})
-      SET(PLUGIN_PATH "$ENV{HDF5_PLUGIN_PATH}")
-    ELSE()
+# Ensure no defined plugin dir if not enabled
+IF(NOT ENABLE_PLUGIN_INSTALL)
+    UNSET(PLUGIN_INSTALL_DIR CACHE)
+ENDIF()
+
+IF(ENABLE_PLUGIN_INSTALL)
+    IF(NOT DEFINED PLUGIN_INSTALL_DIR)
+      # Default to HDF5_PLUGIN_PATH or its default directories
+      IF(DEFINED ENV{HDF5_PLUGIN_PATH})
+        SET(PLUGIN_INSTALL_DIR "$ENV{HDF5_PLUGIN_PATH}")
+      ELSE()
         IF(ISMSVC OR ISMINGW)
-	  SET(PLUGIN_PATH "$ENV{ALLUSERSPROFILE}\\hdf5\\lib\\plugin")
+	  SET(PLUGIN_INSTALL_DIR "$ENV{ALLUSERSPROFILE}\\hdf5\\lib\\plugin")
 	ELSE()
-	  SET(PLUGIN_PATH "/usr/local/hdf5/lib/plugin")
+	  SET(PLUGIN_PLUGIN_DIR "/usr/local/hdf5/lib/plugin")
 	ENDIF()
+      ENDIF()
+        MESSAGE("Defaulting to -DPLUGIN_INSTALL_DIR=${PLUGIN_INSTALL_DIR}")
     ENDIF()
 ENDIF()
 
 IF(ENABLE_PLUGIN_INSTALL)
   # Use the lowest priority dir in the path
   IF(NOT ISMSVC AND NOT ISMINGW)
-    STRING(REPLACE ":" ";" PATH_LIST ${PLUGIN_PATH})
+    STRING(REPLACE ":" ";" PATH_LIST ${PLUGIN_INSTALL_DIR})
   ELSE()
-    SET(PATH_LIST ${PLUGIN_PATH})
+    SET(PATH_LIST ${PLUGIN_INSTALL_DIR})
   ENDIF()
 
   # Get last element
   LIST(GET PATH_LIST -1 PLUGIN_INSTALL_DIR)
-  MESSAGE("Defaulting to -DPLUGIN_INSTALL_DIR=${PLUGIN_INSTALL_DIR}")
   SET(PLUGIN_INSTALL_DIR_SETTING "${PLUGIN_INSTALL_DIR}")
+  MESSAGE("Final value of-DPLUGIN_INSTALL_DIR=${PLUGIN_INSTALL_DIR}")
 ELSE() # No option specified
     UNSET(PLUGIN_INSTALL_DIR)
     UNSET(PLUGIN_INSTALL_DIR CACHE)
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index a28e135e29..4a44c42072 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -5,10 +5,9 @@ Release Notes       {#RELEASE_NOTES}
 
 This file contains a high-level description of this package's evolution. Releases are in reverse chronological order (most recent first). Note that, as of netcdf 4.2, the `netcdf-c++` and `netcdf-fortran` libraries have been separated into their own libraries.
 
-
 ## 4.9.1 - T.B.D.
 
-* [Enhancement] Add `--disable-quantize` option to `configure`.
+* [Bug Fix] Fix CMakeLists.txt to handle all acceptable boolean values for -DPLUGIN_INSTALL_DIR. See [Github #2430](https://github.com/Unidata/netcdf-c/pull/2430).
 * [Enhancement] Provide a simple API to allow user access to the internal .rc file table: supports get/set/overwrite of entries of the form "key=value". See [Github #2408](https://github.com/Unidata/netcdf-c/pull/2408).
 * [Bug Fix] Use env variable USERPROFILE instead of HOME for windows and mingw. See [Github #2405](https://github.com/Unidata/netcdf-c/pull/2405).
 * [Bug Fix] Fix the nc_def_var_fletcher32 code in hdf5 to properly test value of the fletcher32 argument. See [Github #2403](https://github.com/Unidata/netcdf-c/pull/2403).
@@ -23,6 +22,7 @@ This file contains a high-level description of this package's evolution. Release
 * [Enhancement] Allow the read/write of JSON-valued Zarr attributes to allow
 for domain specific info such as used by GDAL/Zarr. See [Github #2278](https://github.com/Unidata/netcdf-c/pull/2278).
 * [Enhancement] Turn on the XArray convention for NCZarr files by default. WARNING, this means that the mode should explicitly specify "nczarr" or "zarr" even if "xarray" or "noxarray" is specified. See [Github #2257](https://github.com/Unidata/netcdf-c/pull/2257).
+
 * [Enhancement] Update the documentation to match the current filter capabilities. See [Github #2249](https://github.com/Unidata/netcdf-c/pull/2249).
 * [Enhancement] Support installation of pre-built standard filters into user-specified location. See [Github #2318](https://github.com/Unidata/netcdf-c/pull/2318).
 * [Enhancement] Improve filter support. More specifically (1) add nc_inq_filter_avail to check if a filter is available, (2) add the notion of standard filters, (3) cleanup szip support to fix interaction with NCZarr. See [Github #2245](https://github.com/Unidata/netcdf-c/pull/2245).
@@ -193,7 +193,7 @@ See [GitHub #1251](https://github.com/Unidata/netcdf-c/issues/1251).
 * Fix of --enable-benchmark benchmark tests [Github #1211](https://github.com/Unidata/netcdf-c/issues/1211)
 * Update the license from the home-brewed NetCDF license to the standard 3-Clause BSD License.  This change does not result in any new restrictions; it is merely the adoption of a standard, well-known and well-understood license in place of the historic NetCDF license written at Unidata.  This is part of a broader push by Unidata to adopt modern, standardized licensing.
 * [BugFix] Corrected DAP-related issues on big-endian machines. See [Github #1321](https://github.com/Unidata/netcdf-c/issues/1321), [Github #1302](https://github.com/Unidata/netcdf-c/issues/1302) for more information.
-* [BugFix][Enhancement]  Various and sundry bugfixes and performance enhancements, thanks to \@edhartnett, \@gsjaardema, \@t-b, \@wkliao, and all of our other contributors.
+* [BugFix][Enhancement]  Various and sundry bugfixes and performance enhancements, thanks to \@edhartnett, \@gsjarrdema, \@t-b, \@wkliao, and all of our other contributors.
 * [Enhancement] Extended `nccopy -F` syntax to support multiple variables with a single invocation. See [Github #1311](https://github.com/Unidata/netcdf-c/issues/1311) for more information.
 * [BugFix] Corrected an issue where DAP2 was incorrectly converting signed bytes, resulting in an erroneous error message under some circumstances. See [GitHub #1317](https://github.com/Unidata/netcdf-c/issues/1317) for more information.  See [Github #1319](https://github.com/Unidata/netcdf-c/issues/1319) for related information.
 * [BugFix][Enhancement] Modified `nccopy` so that `_NCProperties` is not copied over verbatim but is instead generated based on the version of `libnetcdf` used when copying the file.  Additionally, `_NCProperties` are displayed if/when associated with a netcdf3 file, now. See [GitHub #803](https://github.com/Unidata/netcdf-c/issues/803) for more information.
diff --git a/nc_test4/tst_specific_filters.sh b/nc_test4/tst_specific_filters.sh
index 43235d2869..64074b04c5 100755
--- a/nc_test4/tst_specific_filters.sh
+++ b/nc_test4/tst_specific_filters.sh
@@ -8,6 +8,7 @@
 if test "x$srcdir" = x ; then srcdir=`pwd`; fi
 . ../test_common.sh
 
+set -x
 set -e
 
 if test "x$TESTNCZARR" = x1 ; then