Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -8078,7 +8078,7 @@
   /// Determine whether a particular identifier might be the name in a C++1z
   /// deduction-guide declaration.
   bool isDeductionGuideName(Scope *S, const IdentifierInfo &Name,
-                            SourceLocation NameLoc,
+                            SourceLocation NameLoc, CXXScopeSpec &SS,
                             ParsedTemplateTy *Template = nullptr);
 
   bool DiagnoseUnknownTemplateName(const IdentifierInfo &II,
Index: clang/lib/Parse/ParseDecl.cpp
===================================================================
--- clang/lib/Parse/ParseDecl.cpp
+++ clang/lib/Parse/ParseDecl.cpp
@@ -3696,11 +3696,12 @@
 
       // Likewise, if this is a context where the identifier could be a template
       // name, check whether this is a deduction guide declaration.
+      CXXScopeSpec SS;
       if (getLangOpts().CPlusPlus17 &&
           (DSContext == DeclSpecContext::DSC_class ||
            DSContext == DeclSpecContext::DSC_top_level) &&
           Actions.isDeductionGuideName(getCurScope(), *Tok.getIdentifierInfo(),
-                                       Tok.getLocation()) &&
+                                       Tok.getLocation(), SS) &&
           isConstructorDeclarator(/*Unqualified*/ true,
                                   /*DeductionGuide*/ true))
         goto DoneWithDeclSpec;
Index: clang/lib/Parse/ParseExprCXX.cpp
===================================================================
--- clang/lib/Parse/ParseExprCXX.cpp
+++ clang/lib/Parse/ParseExprCXX.cpp
@@ -2913,7 +2913,7 @@
       Result.setConstructorName(Ty, IdLoc, IdLoc);
     } else if (getLangOpts().CPlusPlus17 &&
                AllowDeductionGuide && SS.isEmpty() &&
-               Actions.isDeductionGuideName(getCurScope(), *Id, IdLoc,
+               Actions.isDeductionGuideName(getCurScope(), *Id, IdLoc, SS,
                                             &TemplateName)) {
       // We have parsed a template-name naming a deduction guide.
       Result.setDeductionGuideName(TemplateName, IdLoc);
Index: clang/lib/Parse/ParseTentative.cpp
===================================================================
--- clang/lib/Parse/ParseTentative.cpp
+++ clang/lib/Parse/ParseTentative.cpp
@@ -76,7 +76,7 @@
         IdentifierInfo *II = Tok.getIdentifierInfo();
         bool isDeductionGuide =
             Actions.isDeductionGuideName(getCurScope(), *II, Tok.getLocation(),
-                                         /*Template=*/nullptr);
+                                         SS, /*Template=*/nullptr);
         if (Actions.isCurrentClassName(*II, getCurScope(), &SS) ||
             isDeductionGuide) {
           if (isConstructorDeclarator(/*Unqualified=*/SS.isEmpty(),
Index: clang/lib/Sema/SemaTemplate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplate.cpp
+++ clang/lib/Sema/SemaTemplate.cpp
@@ -316,9 +316,8 @@
 }
 
 bool Sema::isDeductionGuideName(Scope *S, const IdentifierInfo &Name,
-                                SourceLocation NameLoc,
-                                ParsedTemplateTy *Template) {
-  CXXScopeSpec SS;
+                                SourceLocation NameLoc, CXXScopeSpec &SS,
+                                ParsedTemplateTy *Template/*=nullptr*/) {
   bool MemberOfUnknownSpecialization = false;
 
   // We could use redeclaration lookup here, but we don't need to: the
Index: clang/test/Interpreter/disambiguate-decl-stmt.cpp
===================================================================
--- clang/test/Interpreter/disambiguate-decl-stmt.cpp
+++ clang/test/Interpreter/disambiguate-decl-stmt.cpp
@@ -7,6 +7,10 @@
 
 // Decls which are hard to disambiguate
 
+// Templates
+namespace ns1 { template<typename T> void tmplt(T &) {}}
+int arg_tmplt = 12; ns1::tmplt(arg_tmplt);
+
 // ParseStatementOrDeclaration returns multiple statements.
 #ifdef MS
 int g_bFlag = 1;