diff --git a/sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/OperandMerging.java b/sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/OperandMerging.java
index b1f4e233192..4882ddc17b0 100644
--- a/sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/OperandMerging.java
+++ b/sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/OperandMerging.java
@@ -69,10 +69,18 @@ void mergeOutput(@Nonnull Operand outputOperand) {
     if (output == null) {
       output = outputOperand;
     } else if (output.stackLocal != null) {
-      if (output.stackLocal != outputOperand.stackLocal && outputOperand.stackLocal != null) {
-        throw new IllegalStateException("Incompatible StackLocals. There already exists more than one StackLocal (" + outputOperand.stackLocal + " != " + output.stackLocal+").");
+      if (outputOperand.stackLocal == null) {
+        outputOperand.changeStackLocal(output.stackLocal);
+      } else {
+        if (output.stackLocal != outputOperand.stackLocal) {
+          throw new IllegalStateException(
+              "Incompatible stacklocal mismatch. There exist multiple, different possible output Locals ("
+                  + outputOperand.stackLocal
+                  + ", "
+                  + output.stackLocal
+                  + ").");
+        }
       }
-      outputOperand.changeStackLocal(output.stackLocal);
     }
   }