diff --git a/sv-parser-pp/src/preprocess.rs b/sv-parser-pp/src/preprocess.rs
index caa686e..d79061c 100644
--- a/sv-parser-pp/src/preprocess.rs
+++ b/sv-parser-pp/src/preprocess.rs
@@ -1618,4 +1618,21 @@ mod tests {
             testfile_contents("unconnected_drive.sv")
         );
     } // }}}
+
+    #[test]
+    fn undef() { // {{{
+        let include_paths = [testfile_path("")];
+        let (ret, _) = preprocess(
+            testfile_path("undef.sv"),
+            &HashMap::new(),
+            &include_paths,
+            false,
+            false,
+        )
+        .unwrap();
+        assert_eq!(
+            ret.text(),
+            testfile_contents("expected/undef.sv")
+        );
+    } // }}}
 }
diff --git a/sv-parser-pp/testcases/expected/undef.sv b/sv-parser-pp/testcases/expected/undef.sv
new file mode 100644
index 0000000..e0e4eff
--- /dev/null
+++ b/sv-parser-pp/testcases/expected/undef.sv
@@ -0,0 +1,20 @@
+// IEEE1800-2017 Clause 22.5.2
+// The directive `undef shall undefine the specified text macro if previously
+// defined by a `define compiler directive within the compilation unit. An
+// attempt to undefine a text macro that was not previously defined using a
+// `define compiler directive can issue a warning.
+`undef FOO
+`undef FOO// Comment
+`undef FOO // Comment
+
+`define FOO foo
+// AAA
+// This block SHOULD be emitted from the preprocessor.
+
+
+
+`undef FOO
+
+// BBB
+// This block SHOULD be emitted from the preprocessor.
+
diff --git a/sv-parser-pp/testcases/undef.sv b/sv-parser-pp/testcases/undef.sv
new file mode 100644
index 0000000..76d3731
--- /dev/null
+++ b/sv-parser-pp/testcases/undef.sv
@@ -0,0 +1,28 @@
+// IEEE1800-2017 Clause 22.5.2
+// The directive `undef shall undefine the specified text macro if previously
+// defined by a `define compiler directive within the compilation unit. An
+// attempt to undefine a text macro that was not previously defined using a
+// `define compiler directive can issue a warning.
+`undef FOO
+`undef FOO// Comment
+`undef FOO // Comment
+
+`define FOO foo
+`ifdef FOO
+// AAA
+// This block SHOULD be emitted from the preprocessor.
+`endif
+`ifndef FOO
+// AAA
+// This block should NOT be emitted from the preprocessor.
+`endif
+
+`undef FOO
+`ifdef FOO
+// BBB
+// This block should NOT be emitted from the preprocessor.
+`endif
+`ifndef FOO
+// BBB
+// This block SHOULD be emitted from the preprocessor.
+`endif