diff --git a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
index f72a07ab10f..d08b56dbee6 100644
--- a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
+++ b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
@@ -38,6 +38,8 @@ import org.eclipse.cdt.core.CCorePlugin;
 import org.eclipse.cdt.core.testplugin.TestScannerProvider;
 import org.eclipse.cdt.core.testplugin.util.BaseTestCase;
 
+import org.eclipse.cdt.internal.ui.text.contentassist.CCompletionProposal;
+
 /**
  * A collection of code completion tests.
  *
@@ -1660,6 +1662,17 @@ public class CompletionTests extends CompletionTestBase {
 		}
 	}
 	
+	//	void foo(int x, int y);
+	//	void caller() {
+	//		fo/*cursor*/
+	//	}
+	public void testReplacementLength_511274() throws Exception {
+		Object[] results = invokeContentAssist(fCursorOffset, 0, true, false, true).results;
+		assertEquals(1, results.length);
+		assertInstance(results[0], CCompletionProposal.class);
+		assertEquals(2, ((CCompletionProposal) results[0]).getReplacementLength());
+	}
+	
 	//	struct A {
 	//	    void foo();
 	//	};
diff --git a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/text/contentassist/ParameterGuessingProposal.java b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/text/contentassist/ParameterGuessingProposal.java
index 07112a21168..f27d3c5780b 100644
--- a/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/text/contentassist/ParameterGuessingProposal.java
+++ b/core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/text/contentassist/ParameterGuessingProposal.java
@@ -113,7 +113,7 @@ public class ParameterGuessingProposal extends FunctionCompletionProposal {
 			replacement = fullPrefix + replacement + ")"; //$NON-NLS-1$
 			replacementOffset = proposal.getReplacementOffset();
 		}
-		replacementLength = replacement.length();
+		replacementLength = prefix.length();
 		ParameterGuessingProposal ret = new ParameterGuessingProposal(replacement, replacementOffset,
 				replacementLength, proposal.getImage(), proposal.getDisplayString(), proposal.getIdString(),
 				proposal.getRelevance(), context.getViewer(), function, invocationOffset, parseOffset,