diff --git a/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/ResolveTests12To15.java b/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/ResolveTests12To15.java
index f05551545fe..d1624bbfa7a 100644
--- a/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/ResolveTests12To15.java
+++ b/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/ResolveTests12To15.java
@@ -916,4 +916,43 @@ public void testBug577508_4() throws JavaModelException {
 		elements
 	);
 }
+// https://github.com/eclipse-jdt/eclipse.jdt.core/issues/1278
+// Wrong method redirect
+public void testGH1278() throws JavaModelException {
+	this.wc = getWorkingCopy("/Resolve15/src/TestSelect.java",
+					"public class TestSelect {\n" +
+	                "    class Integer {}\n" +
+					"    class Double {}\n" +
+					"\n" +
+					"	public void foo(String s) {\n" +
+					"\n" +
+					"	}\n" +
+					"\n" +
+					"	public void foo(Integer i) {\n" +
+					"\n" +
+					"	}\n" +
+					"\n" +
+					"	public void foo(Double d) {\n" +
+					"\n" +
+					"	}\n" +
+					"\n" +
+					"	public void foo2(Integer i) {\n" +
+					"		Object test = 1d;\n" +
+					"		if (test instanceof Double test2) {\n" +
+					"			foo(test2);\n" +
+					"		}\n" +
+					"	}\n" +
+					"\n" +
+					"}\n");
+	String str = this.wc.getSource();
+	String selection = "foo";
+	int start = str.lastIndexOf(selection);
+	int length = selection.length();
+	IJavaElement[] elements = this.wc.codeSelect(start, length);
+	assertElementsEqual(
+		"Unexpected elements",
+		"foo(Double) [in TestSelect [in [Working copy] TestSelect.java [in <default> [in src [in Resolve15]]]]]",
+		elements
+	);
+}
 }
diff --git a/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/select/SelectionParser.java b/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/select/SelectionParser.java
index 1013efbf702..d8187a0df5d 100644
--- a/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/select/SelectionParser.java
+++ b/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/select/SelectionParser.java
@@ -35,6 +35,7 @@
 import org.eclipse.jdt.internal.compiler.ast.Annotation;
 import org.eclipse.jdt.internal.compiler.ast.Argument;
 import org.eclipse.jdt.internal.compiler.ast.ArrayAllocationExpression;
+import org.eclipse.jdt.internal.compiler.ast.Block;
 import org.eclipse.jdt.internal.compiler.ast.CaseStatement;
 import org.eclipse.jdt.internal.compiler.ast.CastExpression;
 import org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration;
@@ -249,11 +250,38 @@ private void buildMoreCompletionContext(Expression expression) {
 			wrapInIf = true;
 			orphan = right;
 		} else if (this.elementKindStack[i] == K_INSIDE_ELSE_STATEMENT) {
+			int newAstPtr = this.elementInfoStack[i];
+			int length = this.astPtr - newAstPtr;
+			Statement[] statements = new Statement[length+1];
+			System.arraycopy(
+				this.astStack,
+				newAstPtr + 1,
+				statements,
+				0,
+				length);
+			statements[length] = orphan;
+			this.astPtr = newAstPtr;
+			Block b = new Block(0);
+			b.statements = statements;
+			elseStat = b;
 			thenStat = (Statement) this.astStack[this.elementInfoStack[i]];
-			elseStat = orphan;
+			this.astPtr--;
 		} else if (this.elementKindStack[i] == K_INSIDE_THEN_STATEMENT) {
 			Expression e = this.expressionStack[this.elementInfoStack[i]];
-			if (thenStat == null) thenStat = orphan;
+			int newAstPtr = (int) this.elementObjectInfoStack[i];
+			int length = this.astPtr - newAstPtr;
+			Statement[] statements = new Statement[length+1];
+			System.arraycopy(
+				this.astStack,
+				newAstPtr + 1,
+				statements,
+				0,
+				length);
+			statements[length] = orphan;
+			this.astPtr = newAstPtr;
+			Block b = new Block(0);
+			b.statements = statements;
+			if (thenStat == null) thenStat = b;
 			parentNode = orphan = new IfStatement(e, thenStat, elseStat, 0, 0);
 		}
 		i--;
@@ -834,7 +862,7 @@ protected void consumeGuard() {
 @Override
 protected void consumePostIfExpression() {
 	super.consumePostIfExpression();
-	pushOnElementStack(K_INSIDE_THEN_STATEMENT, this.expressionPtr);
+	pushOnElementStack(K_INSIDE_THEN_STATEMENT, this.expressionPtr, this.astPtr);
 }
 
 @Override
@@ -1936,6 +1964,8 @@ protected int astPtr() {
 	for (int i = 0; i <= this.elementPtr; i++) {
 		if (this.elementKindStack[i] == K_INSIDE_SWITCH)
 			return (int) this.elementObjectInfoStack[i];
+		else if (this.elementKindStack[i] == K_INSIDE_THEN_STATEMENT)
+			return (int) this.elementObjectInfoStack[i];
 	}
 	return super.astPtr();
 }