diff --git a/lib/data/odata-filter.js b/lib/data/odata-filter.js
index b9b80756e..397749c47 100644
--- a/lib/data/odata-filter.js
+++ b/lib/data/odata-filter.js
@@ -24,13 +24,18 @@ const odataFilter = (expr, odataToColumnMap) => {
   // I don't want to pass it to all of them.
 
   const extractFunctions = ['year', 'month', 'day', 'hour', 'minute', 'second'];
-  const methodCall = (fn, params) => {
+  const methodCall = (node) => {
     // n.b. odata-v4-parser appears to already validate function name and arity.
+    const fn = node.value.method;
     const lowerName = fn.toLowerCase();
-    if (extractFunctions.includes(lowerName))
+    const params = node.value.parameters;
+    if (extractFunctions.includes(lowerName)) {
       return sql`extract(${raw(lowerName)} from ${op(params[0])})`; // eslint-disable-line no-use-before-define
-    else if (fn === 'now')
+    } else if (fn === 'now') {
       return sql`now()`;
+    } else {
+      throw Problem.internal.unsupportedODataExpression({ at: node.position, type: node.type, text: node.raw });
+    }
   };
   const binaryOp = (left, right, operator) =>
     // always use parens to ensure the original AST op precedence.
@@ -51,7 +56,7 @@ const odataFilter = (expr, odataToColumnMap) => {
         : (/^'.*'$/.test(node.raw)) ? node.raw.slice(1, node.raw.length - 1)
           : node.raw; // eslint-disable-line indent
     } else if (node.type === 'MethodCallExpression') {
-      return methodCall(node.value.method, node.value.parameters);
+      return methodCall(node);
     } else if (node.type === 'EqualsExpression') {
       return binaryOp(node.value.left, node.value.right, 'is not distinct from');
     } else if (node.type === 'NotEqualsExpression') {
diff --git a/test/assertions.js b/test/assertions.js
index 0ba7db4f5..facce83d9 100644
--- a/test/assertions.js
+++ b/test/assertions.js
@@ -227,6 +227,14 @@ should.Assertion.add('FormAttachment', function() {
   if (this.obj.updatedAt != null) this.obj.updatedAt.should.be.an.isoDate();
 });
 
+should.Assertion.add('Problem', function() {
+  this.params = { operator: 'to be a Problem' };
+
+  this.obj.should.be.a.Error();
+  Object.keys(this.obj).should.containDeep([ 'problemCode', 'problemDetails' ]);
+  this.obj.problemCode.should.be.a.Number();
+});
+
 should.Assertion.add('Project', function() {
   this.params = { operator: 'to be a Project' };
 
diff --git a/test/unit/data/odata-filter.js b/test/unit/data/odata-filter.js
index 2aae786da..120eea6a9 100644
--- a/test/unit/data/odata-filter.js
+++ b/test/unit/data/odata-filter.js
@@ -74,6 +74,15 @@ describe('OData filter query transformer', () => {
       return true;
     });
   });
+
+  it('should reject unrecognized function names', () => {
+    assert.throws(() => { odataFilter('123 eq trim(\' 123 \')'); }, (err) => {
+      err.should.be.a.Problem();
+      err.problemCode.should.equal(501.4);
+      err.message.should.equal('The given OData filter expression uses features not supported by this server: MethodCallExpression at 7 ("trim(\' 123 \')")');
+      return true;
+    });
+  });
 });
 
 describe('OData orderby/sort query transformer', () => {