diff --git a/codan/org.eclipse.cdt.codan.checkers/src/org/eclipse/cdt/codan/internal/checkers/AssignmentToItselfChecker.java b/codan/org.eclipse.cdt.codan.checkers/src/org/eclipse/cdt/codan/internal/checkers/AssignmentToItselfChecker.java
index f672f8f4f24..09d1a330492 100644
--- a/codan/org.eclipse.cdt.codan.checkers/src/org/eclipse/cdt/codan/internal/checkers/AssignmentToItselfChecker.java
+++ b/codan/org.eclipse.cdt.codan.checkers/src/org/eclipse/cdt/codan/internal/checkers/AssignmentToItselfChecker.java
@@ -44,7 +44,12 @@ public class AssignmentToItselfChecker extends AbstractIndexAstChecker {
 				if (e instanceof IASTBinaryExpression) {
 					IASTBinaryExpression binExpr = (IASTBinaryExpression) e;
 					if (binExpr.getOperator() == IASTBinaryExpression.op_assign) {
-						return binExpr.getOperand1().getRawSignature().equals(binExpr.getOperand2().getRawSignature());
+						String op1 = binExpr.getOperand1().getRawSignature();
+						String op2 = binExpr.getOperand2().getRawSignature();
+						String expr = binExpr.getRawSignature();
+						return op1.equals(op2)
+						  // when macro is used RawSignature returns macro name, see Bug 321933
+						  && !op1.equals(expr);
 					}
 				}
 				return false;
diff --git a/codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/internal/checkers/AssignmentToItselfCheckerTest.java b/codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/internal/checkers/AssignmentToItselfCheckerTest.java
index e4e14848a23..bbf1f05d4b1 100644
--- a/codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/internal/checkers/AssignmentToItselfCheckerTest.java
+++ b/codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/internal/checkers/AssignmentToItselfCheckerTest.java
@@ -54,4 +54,14 @@ public class AssignmentToItselfCheckerTest extends CheckerTestCase {
 		loadCodeAndRun(getAboveComment());
 		checkErrorLine(4);
 	}
+
+	// #define X a = 1
+	// void main() {
+	//    int a;
+	//    X;
+	// }
+	public void testNoError_Bug321933() {
+		loadCodeAndRun(getAboveComment());
+		checkNoErrors();
+	}
 }