diff --git a/bin/foamEtcFile b/bin/foamEtcFile
index 0a31ed9c48..5073744218 100755
--- a/bin/foamEtcFile
+++ b/bin/foamEtcFile
@@ -68,6 +68,7 @@ options:
   -config           Add config directory prefix for shell type:
                         with -csh* for a config.csh/ prefix
                         with -sh*  for a config.sh/ prefix
+  -etc=[DIR]        set/unset FOAM_CONFIG_ETC for alternative etc directory
   -show-api         Print META-INFO api value and exit
   -show-patch       Print META-INFO patch value and exit
   -with-api=NUM     Specify alternative api value to search with
@@ -118,15 +119,6 @@ optMode=ugo                                         # Default search = 'ugo'
 # Environment overrides
 case "$FOAM_CONFIG_MODE" in ([ugo]*) optMode="$FOAM_CONFIG_MODE" ;; esac
 
-# Verify validity of FOAM_CONFIG_ETC
-if [ -n "$FOAM_CONFIG_ETC" ]
-then
-    if [ ! -d "$FOAM_CONFIG_ETC" ] || [ "$FOAM_CONFIG_ETC" = "$projectDir/etc" ]
-    then
-        # Bad directory or redundant value
-        unset FOAM_CONFIG_ETC
-    fi
-fi
 
 #-------------------------------------------------------------------------------
 
@@ -211,6 +203,10 @@ do
         optSilent=true
         ;;
 
+    -etc=*)
+        # FOAM_CONFIG_ETC for finding files. Empty unsets it (later)
+        export FOAM_CONFIG_ETC="${1#*=}"
+        ;;
     -prefix=* | -version=*)
         echo "ignored defunct option '${1%%=*}'" 1>&2
         ;;
@@ -237,6 +233,23 @@ done
 
 #-------------------------------------------------------------------------------
 
+# Verify FOAM_CONFIG_ETC
+if [ -n "$FOAM_CONFIG_ETC" ]
+then
+    if [ "$FOAM_CONFIG_ETC" = "etc" ] \
+    || [ "$FOAM_CONFIG_ETC" = "$projectDir/etc" ]
+    then
+        # Redundant value
+        unset FOAM_CONFIG_ETC
+    elif [ "${FOAM_CONFIG_ETC#/}" = "$FOAM_CONFIG_ETC" ]
+    then
+        # Relative to project-dir
+        FOAM_CONFIG_ETC="$projectDir/$FOAM_CONFIG_ETC"
+    fi
+else
+    unset FOAM_CONFIG_ETC
+fi
+
 # Establish the API value
 [ -n "$projectApi" ] || projectApi=$(getApiInfo api)
 
diff --git a/bin/tools/foamConfigurePaths b/bin/tools/foamConfigurePaths
index 03859f4ce7..27677be6bb 100755
--- a/bin/tools/foamConfigurePaths
+++ b/bin/tools/foamConfigurePaths
@@ -71,7 +71,7 @@ Options
   -help-full          Display full help and exit
 
 Basic
-  -etc=DIR            set FOAM_CONFIG_ETC for alternative project files
+  -etc=[DIR]          set/unset FOAM_CONFIG_ETC for alternative project files
   -project-path DIR   specify 'WM_PROJECT_DIR' (eg, /opt/openfoam1806-patch1)
   -version VER        specify project version (eg, v1806)
   -sp | -SP | -float32 single precision (WM_PRECISION_OPTION)
@@ -416,8 +416,9 @@ CONFIG_CSH
 ## Basic ##
 
    -etc=*)
-        # Define FOAM_CONFIG_ETC for finding files
+        # FOAM_CONFIG_ETC for finding files. Empty unsets it
         export FOAM_CONFIG_ETC="${1#*=}"
+        [ -n "$FOAM_CONFIG_ETC" ] || unset FOAM_CONFIG_ETC
         ;;
 
    -project-path)
diff --git a/etc/config.csh/setup b/etc/config.csh/setup
index 0d43ccb033..5f9bec387f 100644
--- a/etc/config.csh/setup
+++ b/etc/config.csh/setup
@@ -127,12 +127,10 @@ while ( $#argv > 0 )
     shift
 end
 
-# The prefs may have injected a FOAM_CONFIG_ETC value.
-# Verify that it makes sense before continuing.
+# Verify FOAM_CONFIG_ETC (from calling environment or from prefs)
 if ( $?FOAM_CONFIG_ETC ) then
-    if ( ! -d "$FOAM_CONFIG_ETC" ) then
-        echo "Ignore invalid FOAM_CONFIG_ETC = $FOAM_CONFIG_ETC"
-    else if ( "$FOAM_CONFIG_ETC" == "$WM_PROJECT_DIR/etc" ) then
+    if ( "$FOAM_CONFIG_ETC" == "etc" || "$FOAM_CONFIG_ETC" == "$WM_PROJECT_DIR/etc" ) then
+        # Redundant value
         unsetenv FOAM_CONFIG_ETC
     endif
 endif
diff --git a/etc/config.sh/setup b/etc/config.sh/setup
index 48287d4f06..ed4df86dbf 100644
--- a/etc/config.sh/setup
+++ b/etc/config.sh/setup
@@ -115,19 +115,19 @@ else
     _foamEval "$@"
 fi
 
-# The prefs may have injected a FOAM_CONFIG_ETC value.
-# Verify that it makes sense before continuing.
+# Verify FOAM_CONFIG_ETC (from calling environment or from prefs)
 if [ -n "$FOAM_CONFIG_ETC" ]
 then
-    if [ ! -d "$FOAM_CONFIG_ETC" ]
-    then
-        echo "Ignore invalid FOAM_CONFIG_ETC = $FOAM_CONFIG_ETC" 1>&2
-        unset FOAM_CONFIG_ETC
-    elif [ "$FOAM_CONFIG_ETC" = "$WM_PROJECT_DIR/etc" ]
+    if [ "$FOAM_CONFIG_ETC" = "etc" ] \
+    || [ "$FOAM_CONFIG_ETC" = "$WM_PROJECT_DIR/etc" ]
     then
         # Redundant value
         unset FOAM_CONFIG_ETC
+    else
+        export FOAM_CONFIG_ETC
     fi
+else
+    unset FOAM_CONFIG_ETC
 fi