diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 787a485e0b2f8..d544cfac55ba3 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -5184,6 +5184,7 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
 
     ParmVarDecl *Parm = Function->getParamDecl(0);
     TypeSourceInfo *NewParmSI = IR.TransformType(Parm->getTypeSourceInfo());
+    assert(NewParmSI && "Type transformation failed.");
     Parm->setType(NewParmSI->getType());
     Parm->setTypeSourceInfo(NewParmSI);
   };