diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index dd913f935bac..5e7f6523cd86 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -5832,14 +5832,22 @@ void LoopVectorizationCostModel::setVectorizedCallDecision(ElementCount VF) {
       // assumed to be vectors, so we need to extract individual elements from
       // there, execute VF scalar calls, and then gather the result into the
       // vector return value.
-      InstructionCost ScalarCallCost =
-          TTI.getCallInstrCost(ScalarFunc, ScalarRetTy, ScalarTys, CostKind);
+      if (VF.isFixed()) {
+        InstructionCost ScalarCallCost =
+            TTI.getCallInstrCost(ScalarFunc, ScalarRetTy, ScalarTys, CostKind);
 
-      // Compute costs of unpacking argument values for the scalar calls and
-      // packing the return values to a vector.
-      InstructionCost ScalarizationCost = getScalarizationOverhead(CI, VF);
+        // Compute costs of unpacking argument values for the scalar calls and
+        // packing the return values to a vector.
+        InstructionCost ScalarizationCost = getScalarizationOverhead(CI, VF);
+        ScalarCost = ScalarCallCost * VF.getKnownMinValue() + ScalarizationCost;
+      } else {
+        // There is no point attempting to calculate the scalar cost for a
+        // scalable VF as we know it will be Invalid.
+        assert(!getScalarizationOverhead(CI, VF).isValid() &&
+               "Unexpected valid cost for scalarizing scalable vectors");
+        ScalarCost = InstructionCost::getInvalid();
+      }
 
-      ScalarCost = ScalarCallCost * VF.getKnownMinValue() + ScalarizationCost;
       // Honor ForcedScalars and UniformAfterVectorization decisions.
       // TODO: For calls, it might still be more profitable to widen. Use
       // VPlan-based cost model to compare different options.