diff --git a/utils/expr_grammar/grammar.js b/utils/expr_grammar/grammar.js
index 827e278ba..96ceac937 100644
--- a/utils/expr_grammar/grammar.js
+++ b/utils/expr_grammar/grammar.js
@@ -112,6 +112,10 @@ var grammar = {
     {"name": "N", "symbols": ["N$string$18", "_", {"literal":"("}, "_", "P0", "_", {"literal":","}, "_", "P0", "_", {"literal":","}, "_", "P0", "_", {"literal":")"}], "postprocess": function(d) { return window.qwc2ExpressionParserContext.getFeature(d[4], d[8], d[12]); }},
     {"name": "N$string$19", "symbols": [{"literal":"g"}, {"literal":"e"}, {"literal":"t"}, {"literal":"_"}, {"literal":"f"}, {"literal":"e"}, {"literal":"a"}, {"literal":"t"}, {"literal":"u"}, {"literal":"r"}, {"literal":"e"}, {"literal":"_"}, {"literal":"b"}, {"literal":"y"}, {"literal":"_"}, {"literal":"i"}, {"literal":"d"}], "postprocess": function joiner(d) {return d.join('');}},
     {"name": "N", "symbols": ["N$string$19", "_", {"literal":"("}, "_", "P0", "_", {"literal":","}, "_", "P0", "_", {"literal":")"}], "postprocess": function(d) { return window.qwc2ExpressionParserContext.getFeature(d[4], "id", d[8]); }},
+    {"name": "N$string$20", "symbols": [{"literal":"C"}, {"literal":"A"}, {"literal":"S"}, {"literal":"E"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "N$string$21", "symbols": [{"literal":"E"}, {"literal":"L"}, {"literal":"S"}, {"literal":"E"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "N$string$22", "symbols": [{"literal":"E"}, {"literal":"N"}, {"literal":"D"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "N", "symbols": ["N$string$20", "_", "when_args", "_", "N$string$21", "_", "P0", "_", "N$string$22"], "postprocess": function(d) { return d[2] !== undefined ? d[2] : d[6]; }},
     {"name": "N$subexpression$1", "symbols": [/[pP]/, /[iI]/], "postprocess": function(d) {return d.join(""); }},
     {"name": "N", "symbols": ["N$subexpression$1"], "postprocess": function(d) { return Math.PI; }},
     {"name": "N$subexpression$2", "symbols": [/[eE]/], "postprocess": function(d) {return d.join(""); }},
@@ -122,8 +126,14 @@ var grammar = {
     {"name": "N", "symbols": ["N$subexpression$4"], "postprocess": function(d) { return false; }},
     {"name": "N$subexpression$5", "symbols": [/[tT]/, /[rR]/, /[uU]/, /[eE]/], "postprocess": function(d) {return d.join(""); }},
     {"name": "N", "symbols": ["N$subexpression$5"], "postprocess": function(d) { return true; }},
-    {"name": "var_args", "symbols": ["P0"], "postprocess": function(d) {return [d[0]];}},
+    {"name": "var_args", "symbols": ["P0"], "postprocess": function(d) { return [d[0]]; }},
     {"name": "var_args", "symbols": ["var_args", "_", {"literal":","}, "_", "P0"], "postprocess": function(d) { return [...d[0], d[4]]; }},
+    {"name": "when_args$string$1", "symbols": [{"literal":"W"}, {"literal":"H"}, {"literal":"E"}, {"literal":"N"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "when_args$string$2", "symbols": [{"literal":"T"}, {"literal":"H"}, {"literal":"E"}, {"literal":"N"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "when_args", "symbols": ["when_args$string$1", "_", "P0", "_", "when_args$string$2", "_", "P0"], "postprocess": function(d) { return d[2] ? d[6] : undefined; }},
+    {"name": "when_args$string$3", "symbols": [{"literal":"W"}, {"literal":"H"}, {"literal":"E"}, {"literal":"N"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "when_args$string$4", "symbols": [{"literal":"T"}, {"literal":"H"}, {"literal":"E"}, {"literal":"N"}], "postprocess": function joiner(d) {return d.join('');}},
+    {"name": "when_args", "symbols": ["when_args", "_", "when_args$string$3", "_", "P0", "_", "when_args$string$4", "_", "P0"], "postprocess": function(d) { return d[0] !== undefined ? d[0] : (d[4] ? d[8] : undefined); }},
     {"name": "float", "symbols": ["int", {"literal":"."}, "int"], "postprocess": function(d) { return parseFloat(d[0] + d[1] + d[2])}},
     {"name": "float", "symbols": ["int"], "postprocess": function(d) { return parseInt(d[0])}},
     {"name": "int$ebnf$1", "symbols": [/[0-9]/]},
diff --git a/utils/expr_grammar/grammar.ne b/utils/expr_grammar/grammar.ne
index e97b3cbf5..24dd7a67e 100644
--- a/utils/expr_grammar/grammar.ne
+++ b/utils/expr_grammar/grammar.ne
@@ -73,15 +73,19 @@ N -> float                         {% id %}
     | "attribute" _ "(" _ P0 _ "," _ P0 _ ")"              {% function(d) { return d[4]?.properties?.[d[8]] ?? null; } %}
     | "get_feature" _ "(" _ P0 _ "," _ P0 _ "," _ P0 _ ")" {% function(d) { return window.qwc2ExpressionParserContext.getFeature(d[4], d[8], d[12]); } %}
     | "get_feature_by_id" _ "(" _ P0 _ "," _ P0 _ ")"      {% function(d) { return window.qwc2ExpressionParserContext.getFeature(d[4], "id", d[8]); } %}
+    | "CASE" _ when_args _ "ELSE" _ P0 _ "END"             {% function(d) { return d[2] !== undefined ? d[2] : d[6]; } %}
     | "PI"i                        {% function(d) { return Math.PI; } %}
     | "E"i                         {% function(d) { return Math.E; } %}
     | "NULL"i                      {% function(d) { return null; } %}
     | "FALSE"i                     {% function(d) { return false; } %}
     | "TRUE"i                      {% function(d) { return true; } %}
 
-var_args -> P0 {% function(d) {return [d[0]];} %}
+var_args -> P0                     {% function(d) { return [d[0]]; } %}
 var_args -> var_args _ "," _ P0    {% function(d) { return [...d[0], d[4]]; } %}
 
+when_args -> "WHEN" _ P0 _ "THEN" _ P0             {% function(d) { return d[2] ? d[6] : undefined; } %}
+when_args -> when_args _ "WHEN" _ P0 _ "THEN" _ P0 {% function(d) { return d[0] !== undefined ? d[0] : (d[4] ? d[8] : undefined); } %}
+
 # I use `float` to basically mean a number with a decimal point in it
 float ->
       int "." int                  {% function(d) { return parseFloat(d[0] + d[1] + d[2])} %}