diff --git a/tools/clang/lib/SPIRV/SpirvEmitter.cpp b/tools/clang/lib/SPIRV/SpirvEmitter.cpp
index 75b99e7d09..e3c002c1f8 100644
--- a/tools/clang/lib/SPIRV/SpirvEmitter.cpp
+++ b/tools/clang/lib/SPIRV/SpirvEmitter.cpp
@@ -2539,7 +2539,7 @@ SpirvInstruction *SpirvEmitter::getBaseOfMemberFunction(
 SpirvInstruction *SpirvEmitter::processCall(const CallExpr *callExpr) {
   const FunctionDecl *callee = getCalleeDefinition(callExpr);
 
-  // Note that we always want the defintion because Stmts/Exprs in the
+  // Note that we always want the definition because Stmts/Exprs in the
   // function body references the parameters in the definition.
   if (!callee) {
     emitError("found undefined function", callExpr->getExprLoc());
@@ -2641,7 +2641,7 @@ SpirvInstruction *SpirvEmitter::processCall(const CallExpr *callExpr) {
     const uint32_t argIndex = i + isOperatorOverloading;
 
     // We want the argument variable here so that we can write back to it
-    // later. We will do the OpLoad of this argument manually. So ingore
+    // later. We will do the OpLoad of this argument manually. So ignore
     // the LValueToRValue implicit cast here.
     auto *arg = callExpr->getArg(argIndex)->IgnoreParenLValueCasts();
     const auto *param = callee->getParamDecl(i);
@@ -7771,6 +7771,16 @@ SpirvInstruction *SpirvEmitter::castToFloat(SpirvInstruction *fromVal,
   }
 
   if (isFloatOrVecOfFloatType(fromType)) {
+    uint32_t fromCount = 0;
+    const bool fromIsVec = isVectorType(fromType, nullptr, &fromCount);
+    uint32_t toCount = 0;
+    const bool toIsVec = isVectorType(toFloatType, nullptr, &toCount);
+
+    if (fromIsVec != toIsVec || fromCount != toCount) {
+      emitError("casting from %0 to %1 unsupported", srcLoc) << fromType <<
+          toFloatType;
+      return nullptr;
+    }
     // This is the case of float to float conversion with different bitwidths.
     return convertBitwidth(fromVal, srcLoc, fromType, toFloatType, nullptr,
                            range);
diff --git a/tools/clang/test/CodeGenSPIRV/cast.scalar-to-vec.implicit.hlsl b/tools/clang/test/CodeGenSPIRV/cast.scalar-to-vec.implicit.hlsl
new file mode 100644
index 0000000000..406de72b7d
--- /dev/null
+++ b/tools/clang/test/CodeGenSPIRV/cast.scalar-to-vec.implicit.hlsl
@@ -0,0 +1,18 @@
+// RUN: %dxc -T cs_6_0 -E main
+
+RWTexture2D<float> g_output;
+
+void foo(inout float3 x)
+{
+    x += float3(1, 2, 3);
+}
+
+// CHECK: error: casting from 'float' to 'float3' unsupported
+
+[numthreads(1, 1, 1)]
+void main(uint3 id : SV_DispatchThreadId)
+{
+    float bar = 1;
+    foo(bar);
+    g_output[id.xy] = bar;
+}
diff --git a/tools/clang/unittests/SPIRV/CodeGenSpirvTest.cpp b/tools/clang/unittests/SPIRV/CodeGenSpirvTest.cpp
index fed2885dae..660acaf33d 100644
--- a/tools/clang/unittests/SPIRV/CodeGenSpirvTest.cpp
+++ b/tools/clang/unittests/SPIRV/CodeGenSpirvTest.cpp
@@ -518,6 +518,9 @@ TEST_F(FileTest, CastFlatConversionLiteralInitializer) {
 TEST_F(FileTest, CastFlatConversionDecomposeVector) {
   runFileTest("cast.flat-conversion.vector.hlsl");
 }
+TEST_F(FileTest, CastImplicitScalarToVec) {
+  runFileTest("cast.scalar-to-vec.implicit.hlsl", Expect::Failure);
+}
 TEST_F(FileTest, CastExplicitVecToMat) {
   runFileTest("cast.vec-to-mat.explicit.hlsl");
 }